Toyota electrical-and-engine-control-systems-manual

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  • 1. General Electricity is a form of energy called electrical energy. It is sometimes called an "unseen" force because the energy itself cannot be seen, heard, touched, or smelled. However, the effects of electricity can be seen ... a lamp gives off light; a motor turns; a cigarette lighter gets red hot; a buzzer makes noise. The effects of electricity can also be heard, felt, and smelled. A loud crack of lightning is easily heard, while a fuse "blowing" may sound like a soft "pop" or "snap." With electricity flowing through them, some insulated wires may feel "warm" and bare wires may produce a "tingling" or, worse, quite a "shock." And, of course, the odor of burned wire insulation is easily smelled. ELECTRICAL FUNDAMENTALS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 2. Electron Theory Electron theory helps to explain electricity. The basic building block for matter, anything that has mass and occupies space, is the atom. All matter - solid, liquid, or gas - is made up of molecules, or atoms joined together. These atoms are the smallest particles into which an element or substance can be divided without losing its properties. There are only about 100 different atoms that make up everything in our world. The features that make one atom different from another also determine its electrical properties. ATOMIC STRUCTURE An atom is like a tiny solar system. The center is called the nucleus, made up of tiny particles called protons and neutrons. The nucleus is surrounded by clouds of other tiny particles called electrons. The electrons rotate about the nucleus in fixed paths called shells or rings. Hydrogen has the simplest atom with one proton in the nucleus and one electron rotating around it. Copper is more complex with 29 electrons in four different rings rotating around a nucleus that has 29 protons and 29 neutrons. Other elements have different atomic structures. ELECTRICAL FUNDAMENTALS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 3. ATOMS AND ELECTRICAL CHARGES Each atomic particle has an electrical charge. Electrons have a negative (-) charge. Protons have a positive charge. Neutrons have no charge; they are neutral. In a balanced atom, the number of electrons equals the number of protons. The balance of the opposing negative and positive charges holds the atom together. Like charges repel, unlike charges attract. The positive protons hold the electrons in orbit. Centrifugal force prevents the electrons from moving inward. And, the neutrons cancel the repelling force between protons to hold the atom's core together. POSITIVE AND NEGATIVE IONS If an atom gains electrons, it becomes a negative ion. If an atom loses electrons, it becomes a positive ion. Positive ions attract electrons from neighboring atoms to become balanced. This causes electron flow. ELECTRON FLOW The number of electrons in the outer orbit (valence shell or ring) determines the atom's ability to conduct electricity. Electrons in the inner rings are closer to the core, strongly attracted to the protons, and are called bound electrons. Electrons in the outer ring are further away from the core, less strongly attracted to the protons, and are called free electrons. Electrons can be freed by forces such as friction, heat, light, pressure, chemical action, or magnetic action. These freed electrons move away from the electromotive force, or EMF ("electron moving force"), from one atom to the next. A stream of free electrons forms an electrical current. ELECTRICAL FUNDAMENTALS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 4. CONDUCTORS, INSULATORS, SEMICONDUCTORS The electrical properties of various materials are determined by the number of electrons in the outer ring of their atoms. • CONDUCTORS - Materials with 1 to 3 electrons in the atom's outer ring make good conductors. The electrons are held loosely, there's room for more, and a low EMF will cause a flow of free electrons. • INSULATORS - Materials with 5 to 8 electrons in the atom's outer ring are insulators. The electrons are held tightly, the ring's fairly full, and a very high EMF is needed to cause any electron flow at all. Such materials include glass, rubber, and certain plastics. • SEMICONDUCTORS - Materials with exactly 4 electrons in the atom's outer ring are called semiconductors. They are neither good conductors, nor good insulators. Such materials include carbon, germanium, and silicon. CURRENT FLOW THEORIES Two theories describe current flow. The conventional theory, commonly used for automotive systems, says current flows from (+) to (-) ... excess electrons flow from an area of high potential to one of low potential (-). The electron theory, commonly used for electronics, says current flows from (-) to (+) ... excess electrons cause an area of negative potential (-) and flow toward an area lacking electrons, an area of positive potential (+), to balance the charges. While the direction of current flow makes a difference in the operation of some devices, such as diodes, the direction makes no difference to the three measurable units of electricity: voltage, current, and resistance. ELECTRICAL FUNDAMENTALS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 5. Terms Of Electricity Electricity cannot be weighed on a scale or measured into a container. But, certain electrical "actions" can be measured. These actions or "terms" are used to describe electricity; voltage, current, resistance, and power. VOLTAGE Voltage is electrical pressure, a potential force or difference in electrical charge between two points. It can push electrical current through a wire, but not through its insulation. Voltage is pressure Current is flow. Resistance opposes flow. Power is the amount of work performed. It depends on the amount of pressure and the volume of flow. Voltage is measured in volts. One volt can push a certain amount of current, two volts twice as much, and so on. A voltmeter measures the difference in electrical pressure between two points in volts. A voltmeter is used in parallel. ELECTRICAL FUNDAMENTALS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 6. CURRENT Current is electrical flow moving through a wire. Current flows in a wire pushed by voltage. Current is measured in amperes, or amps, for short. An ammeter measures current flow in amps. It is inserted into the path of current flow, or in series, in a circuit. ELECTRICAL FUNDAMENTALS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 7. RESISTANCE Resistance opposes current flow. It is like electrical "friction." This resistance slows the flow of current. Every electrical component or circuit has resistance. And, this resistance changes electrical energy into another form of energy - heat, light, motion. Resistance is measured in ohms. A special meter, called an ohmmeter, can measure the resistance of a device in ohms when no current is flowing. ELECTRICAL FUNDAMENTALS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 8. Factors Affecting Resistance Five factors determine the resistance of conductors. These factors are length of the conductor, diameter, temperature, physical condition and conductor material. The filament of a lamp, the windings of a motor or coil, and the bimetal elements in sensors are conductors. So, these factors apply to circuit wiring as well as working devices or loads. LENGTH Electrons in motion are constantly colliding as voltage pushes them through a conductor. If two wires are the same material and diameter, the longer wire will have more resistance than the shorter wire. Wire resistance is often listed in ohms per foot (e.g., spark plug cables at 5Ω per foot). Length must be considered when replacing wires. DIAMETER Large conductors allow more current flow with less voltage. If two wires are the same material and length, the thinner wire will have more resistance than the thicker wire. Wire resistance tables list ohms per foot for wires of various thicknesses (e.g., size or gauge ... 1, 2, 3 are thicker with less resistance and more current capacity; 18, 20, 22 are thinner with more resistance and less current capacity). Replacement wires and splices must be the proper size for the circuit current. TEMPERATURE In most conductors, resistance increases as the wire temperature increases. Electrons move faster, but not necessarily in the right direction. Most insulators have less resistance at higher temperatures. Semiconductor devices called thermistors have negative temperature coefficients (NTC) resistance decreases as temperature increases. Toyota's EFI coolant temperature sensor has an NTC thermistor. Other devices use PTC thermistors. PHYSICAL CONDITION Partially cut or nicked wire will act like smaller wire with high resistance in the damaged area. A kink in the wire, poor splices, and loose or corroded connections also increase resistance. Take care not to damage wires during testing or stripping insulation. MATERIAL Materials with many free electrons are good conductors with low resistance to current flow. Materials with many bound electrons are poor conductors (insulators) with high resistance to current flow. Copper, aluminum, gold, and silver have low resistance; rubber, glass, paper, ceramics, plastics, and air have high resistance. ELECTRICAL FUNDAMENTALS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 9. Voltage, Current, And Resistance In Circuits A simple relationship exists between voltage, current, and resistance in electrical circuits. Understanding this relationship is important for fast, accurate electrical problem diagnosis and repair. OHM'S LAW Ohm's Law says: The current in a circuit is directly proportional to the applied voltage and inversely proportional to the amount of resistance. This means that if the voltage goes up, the current flow will go up, and vice versa. Also, as the resistance goes up, the current goes down, and vice versa. Ohm's Law can be put to good use in electrical troubleshooting. But, calculating precise values for voltage, current, and resistance is not always practical ... nor, really needed. A more practical, less time-consuming use of Ohm's Law would be to simply apply the concepts involved: SOURCE VOLTAGE is not affected by either current or resistance. It is either too low, normal, or too high. If it is too low, current will be low. If it is normal, current will be high if resistance is low or current will be low if resistance is high. If voltage is too high, current will be high. CURRENT is affected by either voltage or resistance. If the voltage is high or the resistance is low, current will be high. If the voltage is low or the resistance is high, current will be low. RESISTANCE is not affected by either voltage or current. It is either too low, okay, or too high. If resistance is too low, current will be high at any voltage. If resistance is too high, current will be low if voltage is okay. ELECTRICAL FUNDAMENTALS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 10. ELECTRIC POWER AND WORK Voltage and current are not measurements of electric power and work. Power, in watts, is a measure of electrical energy ... power (P) equals current in amps (1) times voltage in volts (E), P = I x E. Work, in wattseconds or watt-hours, is a measure of the energy used in a period of time ... work equals power in wafts (W) times time in seconds (s) or hours (h), W = P x time. Electrical energy performs work when it is changed into thermal (heat) energy, radiant (light) energy, audio (sound) energy, mechanical (motive) energy, and chemical energy. It can be measured with a waft- hour meter. ELECTRICAL FUNDAMENTALS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 11. Actions Of Current Current flow has the following effects; motion, light or heat generation, chemical reaction, and electromagnetism. HEAT GENERATION When current flows through a lamp filament, defroster grid, or cigarette lighter, heat is generated by changing electrical energy to thermal energy. Fuses melt from the heat generated when too much current flows. CHEMICAL REACTION In a simple battery, a chemical reaction between two different metals and a mixture of acid and water causes a potential energy, or voltage. When the battery is connected to an external load, current will flow. The current will continue flowing until the two metals become similar and the mixture becomes mostly water. When current is sent into the battery by an alternator or a battery charger, however, the reaction is reversed. This is a chemical reaction caused by current flow. The current causes an electrochemical reaction that restores the metals and the acid-water mixture. ELECTROMAGNETISM Electricity and magnetism are closely related. Magnetism can be used to produce electricity. And, electricity can be used to produce magnetism. All conductors carrying current create a magnetic field. The magnetic field strength is changed by changing current ... stronger (more current), weaker (less current). With a straight conductor, the magnetic field surrounds it as a series of circular lines of force. With a looped (coil) conductor, the lines of force can be concentrated to make a very strong field. The field strength can be increased by increasing the current, the number of coil turns, or both. A strong electromagnet can be made by placing an iron core inside a coil. Electromagnetism is used in many ways. ELECTRICAL FUNDAMENTALS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 12. Types Of Electricity There are two types of electricity: static and dynamic. Dynamic electricity can be either direct current (DC) or alternating current (AC). STATIC ELECTRICITY When two non conductors - such as a silk cloth and glass rod - are rubbed together, some electrons are freed. Both materials become electrically charged. One is lacking electrons and is positively charged. The other has extra electrons and is negatively charged. These charges remain on the surface of the material and do not move unless the two materials touch or are connected by a conductor. Since there is no electron flow, this is called static electricity. DYNAMIC ELECTRICITY When electrons are freed from their atoms and flow in a material, this is called dynamic electricity. If the free electrons flow in one direction, the electricity is called direct current (DC). This is the type of current produced by the vehicle's battery. If the free electrons change direction from positive to negative and back repeatedly with time, the electricity is called alternating current (AC). This is the type of current produced by the vehicle's alternator. It is changed to DC for powering the vehicle's electrical system and for charging the battery. ELECTRICAL FUNDAMENTALS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 13. ELECTRICAL FUNDAMENTALS ASSIGNMENT NAME: 1. Describe the atomic structure of an atom and name all it’s components. 2. Explain how an ION differs from an atom. 3. Explain the difference between “bound” and “free” electrons. 4 Explain the function of the “Valence ring” 5. Define the following items: Conductors, Insulators, and Semiconductors. 6. Describe the two theories of electron flow. 7. Define in detail “voltage” and how is it measured. 8. Define in detail “current” and how is it measured. 9. Define in detail “resistance” and how is it measured. 10. Explain the relationship between current and resistance. 11. List and describe the various factors that effect resistance. 12. Explain what ohms law is and how it can be used. 13. Describe the effects of “current flow” through a conductor. 14. Describe in detail the two general categories of “electricity”. 15. Describe the two types of “dynamic electricity”.
  • 14. Electrical Circuits A complete path, or circuit, is needed before voltage can cause a current flow through resistances to perform work. There are several types of circuits, but all require the same basic components. A power source (battery or alternator) produces voltage, or electrical potential. Conductors (wires, printed circuit boards) provide a path for current flow. Working devices, or loads (lamps, motors), change the electrical energy into another form of energy to perform work. Control devices (switches, relays) turn the current flow on and off. And, protection devices (fuses, circuit breakers) interrupt the current path if too much current flows. Too much current is called an overload, which could damage conductors and working devices. A list of five things to look for in any circuit: 1. Source of Voltage 2. Protection Device 3. Load 4. Control 5. Ground We will be identifying these items when we look at Automotive Circuits a little later in this book. ELECTRICAL CIRCUITS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 15. Types Of Circuits There are three basic types of circuits: series, parallel, and series-parallel. The type of circuit is determined by how the power source, conductors, loads, and control or protective devices are connected. SERIES CIRCUIT A series circuit is the simplest circuit. The conductors, control and protection devices, loads, and power source are connected with only one path for current. The resistance of each device can be different. The same amount of current will flow through each. The voltage across each will be different. If the path is broken, no current flows. PARALLEL CIRCUIT A parallel circuit has more than one path for current flow. The same voltage is applied across each branch. If the load resistance in each branch is the same, the current in each branch will be the same. If the load resistance in each branch is different, the current in each branch will be different. If one branch is broken, current will continue flowing to the other branches. SERIES-PARALLEL CIRCUIT A series-parallel circuit has some components in series and others in parallel. The power source and control or protection devices are usually in series; the loads are usually in parallel. The same current flows in the series portion, different currents in the parallel portion. The same voltage is applied to parallel devices, different voltages to series devices. If the series portion is broken, current stops flowing in the entire circuit. If a parallel branch is broken, current continues flowing in the series portion and the remaining branches. ELECTRICAL CIRCUITS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 16. SERIES CIRCUITS In a series circuit, current has only one path. All the circuit components are connected so that the same amount of current flows through each. The circuit must have continuity. If a wire is disconnected or broken, current stops flowing. If one load is open, none of the loads will work. Use of Ohm's Law Applying Ohm's Law to series circuits is easy. Simply add up the load resistances and divide the total resistance into the available voltage to find the current. The voltage drops across the load resistances are then found by multiplying the current by each load resistance. For calculation examples, see page 6 in the Ohms law section. Voltage drop is the difference in voltage (pressure) on one side of a load compared to the voltage on the other side of the load. The drop or loss in voltage is proportional to the amount of resistance. The higher the resistance, the higher the voltage drop. When troubleshooting, then, you can see that more resistance will reduce current and less resistance will increase current. Low voltage would also reduce current and high voltage would increase current. Reduced current will affect component operation (dim lamps, slow motors). But, increased current will also affect component operation (early failure, blown fuses). And, of course, no current at all would mean that the entire circuit would not operate. There are electrical faults that can cause such problems and knowing the relationship between voltage, current, and resistance will help to identify the cause of the problem. ELECTRICAL CIRCUITS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 17. PARALLEL CIRCUITS In a parallel circuit, current can flow through more than one path from and to the power source. The circuit loads are connected in parallel legs, or branches, across a power source. The points where the current paths split and rejoin are called junctions. The separate current paths are called branch circuits or shunt circuits. Each branch operates independent of the others. If one load opens, the others continue operating. Use of Ohm's Law Applying Ohm's Law to parallel circuits is a bit more difficult than with series circuits. The reason is that the branch resistances must be combined to find an equivalent resistance. Just remember that the total resistance in a parallel circuit is less than the smallest load resistance. This makes sense because current can flow through more than one path. Also, remember that the voltage drop across each branch will be the same because the source voltage is applied to each branch. For examples of how to calculate parallel resistance, see page 6. When troubleshooting a parallel circuit, the loss of one or more legs will reduce current because the number of paths is reduced. The addition of one or more legs will increase current because the number of paths is increased. Current can also be reduced by low source voltage or by resistance in the path before the branches. And, current can be increased by high source voltage or by one or more legs being bypassed. High resistance in one leg would affect component operation only in that leg. ELECTRICAL CIRCUITS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 18. SERIES-PARALLEL CIRCUITS In a series-parallel circuit, current flows through the series portion of the circuit and then splits to flow through the parallel branches of the circuit. Some components are wired in series, others in parallel. Most automotive circuits are series- parallel, and the same relationship between voltage, current, and resistance exists. Use of Ohm's Law Applying Ohm's Law to series-parallel circuits is a matter of simply combining the rules seen for series circuits and parallel circuits. First, calculate the equivalent resistance of the parallel loads and add it to the resistances of the loads in series. The total resistance is then divided into the source voltage to find current. Voltage drop across series loads is current times resistance. Current in branches is voltage divided by resistance. For calculation examples, see page 6. When troubleshooting a series-parallel circuit, problems in the series portion can shut down the entire circuit while a problem in one leg of the parallel portion may or may not affect the entire circuit, depending on the problem. Very high resistance in one leg would reduce total circuit current, but increase current in other legs. Very low resistance in one leg would increase total circuit current and possibly have the effect of bypassing other legs. ELECTRICAL CIRCUITS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 19. Ohm's Law Fast, accurate electrical troubleshooting is easy when you know how voltage, current, and resistance are related. Ohm's Law explains the relationship: • Current (amps) equals voltage (volts) divided by resistance (ohms) ... I = E ÷ R. • Voltage (volts) equals current (amps) times resistance (ohms) ... E = I X R. • Resistance (ohms) equals voltage (volts) divided by current (amps) ... R ÷ E = 1. USING OHM'S LAW The effects of different voltages and different resistances on current flow can be seen in the sample circuits. Current found by dividing voltage by resistance. This can be very helpful when diagnosing electrical problems: • When the resistance stays the same ... current goes up as voltage goes up, and current goes down as voltage goes down. A discharged battery has low voltage which reduces current. Some devices may fail to operate (slow motor speed). An unregulated alternator may produce too much voltage which increases current. Some devices may fail early (burned-out lamps). • When the voltage stays the same ... current goes up as resistance goes down, and current goes down as resistance goes up. Bypassed devices reduce resistance, causing high current. Loose connections increase resistance, causing low current. ELECTRICAL CIRCUITS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 20. SAMPLE CALCULATIONS Here are some basic formulas you will find helpful in solving more complex electrical problems. They provide the knowledge required for confidence and thorough understanding of basic electricity. The following abbreviations are used in the formulas: E = VOLTS I = AMPS R = OHMS P = WATTS • Ohm's Law Scientifically stated, it says: "The intensity Of the current in amperes in any electrical circuit is equal to the difference in potential in volts across the circuit divided by the resistance in ohms of the circuit." Simply put it means that current is equal to volts divided by ohms, or expressed as a formula, the law becomes: I = E / R or it can be written: E = I X R This is important because if you know any two of the quantities, the third may be found by applying the equation. Ohm's law includes these two ideas: 1. In a circuit, if resistance is constant, current varies directly with voltage. Now what this means is that if you take a component with a fixed resistance, say a light bulb, and double the voltage you double the current flowing through it. Anyone who has hooked a six- volt bulb to a twelve-volt circuit has experienced this. But it wasn't "too many volts" that burned out the bulb, it was too much current. More about that later. 2. In a circuit, if voltage is constant, current varies inversely with resistance. This second idea states that when resistance goes up, current goes down. That's why corroded connectors cause very dim lights - not enough current. • Watts A watt is an electrical measurement of power or work. It directly relates to horsepower. In fact, in the Sl metric standards that most of the world uses, engine power is given in watts or kilowatts. Electrical power is easily calculated by the formula: P = E X I For instance, a halogen high-beam headlight is rated or 5 amps of current. Figuring 12 volts in the system, we could write: P = E X I P = 12 X 5 P = 60 watts ELECTRICAL CIRCUITS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 21. RESISTANCE The effect of individual resistors on the total resistance of a circuit depends on whether the circuit is series or parallel. Series Circuits In a series circuit, the total resistance is equal to the sum of the individual resistors: SERIES: total R = R1 + R2 + R3 + That is the basis of the concept of voltage drop. For example, if you had a circuit with three loads in series (a bulb, resistor, and corroded ground) you would add the three together to get total resistance. And, of course, the voltage would drop across each load according to its value. Parallel Circuits Parallel circuits are a different story. In a parallel circuit, there are three ways to find total resistance. Method A works in all cases. Method B works only if there are two branches, equal or not. Method C works only if the branches are of equal resistance. A. The total resistance is equal to one over the sum of the reciprocals of the individual resistors. That sounds confusing, but looking at the formula will make it clearer: PARALLEL: n example will make it even clearer. Suppose there is a circuit with three resistors in parallel: 4 ohms, 2 ohms, and 1 ohm. The formula would look like this: That becomes: Which becomes: So there is a little more than one-half ohm resistance in the circuit. You can see that the more resistors in parallel, the less the resistance. In fact, the total resistance is always less than the smallest resistor. This is why a fuse will blow if you add too many circuits to the fuse. There are so many paths for the current to follow that the total resistance of the circuit is very low. That means the current is very high - so high that the fuse can no longer handle the load. B. For two resistors: For a 3 ohm and a 5 ohm resistor that would be: C. For several identical resistors, divide the value of one resistor by the number of resistors, or: Where R1 is the value of one resistor and n is the number of resistors. So if you had three 4 ohm resistors in parallel it would be: ELECTRICAL CIRCUITS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 22. ELECTRICAL CIRCUITS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 23. ELECTRICAL CIRCUITS ASSIGNMENT NAME: 1. Draw and label the parts of a Series Circuit and a Parallel Circuit. 2. Explain the characteristics of “Voltage” and how it differs between a Series Circuit and a Parallel Circuit. 3. Explain the characteristics of “Current” and how it differs between a Series Circuit and a Parallel Circuit. 4. Explain the characteristics of “Resistance” and how it differs between a Series Circuit and a Parallel Circuit.
  • 24. Power Sources On The Car Two power sources are used on Toyota vehicles. When the engine is not running or is being started, the battery provides power. When the engine is running, the alternator provides power for the vehicle's loads and for recharging the battery. THE BATTERY The battery is the primary "source" of electrical energy on Toyota vehicles when the engine is not running or is being started. It uses an electrochemical reaction to change chemical energy into electrical energy for starting, ignition, charging, lighting, and accessories. All Toyota vehicles use a 12-volt battery. Batteries have polarity markings ... the larger (thicker) terminal is marked "plus" or "POS" (+), the other terminal is marked “minus" or "NEG" (-). Correct polarity is important; components can be damaged if the battery is connected backwards. THE ALTERNATOR The alternator is the heart of the vehicle's electrical system when the engine is running. It uses electromagnetism to change some of the engine's mechanical energy into electrical energy for powering the vehicle's loads and for charging the battery. All Toyota alternators are rated by amps of current output ... from 40 to 80 amps. ELECTRICAL COMPONENTS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 25. Loads Working devices - or loads - consume electricity. They change electrical energy into another form of energy to do work. This energy may be thermal (heat), radiant (light), mechanical (motive), audio (sound), chemical, or magnetic. The electrical energy is changed by the resistance of the working device. Resistance is put to work in many ways on Toyota vehicles. PERFORM WORK Some components use resistance to reduce current flow and change electrical energy (voltage) into heat, light, or motion. Resistance produces heat in electric window defrosters and cigarette lighters. Resistance produces light in lamp filaments. And, resistance produces motion in motors and solenoid coils. All circuit loads use resistance to perform work. CONTROL CURRENT Other components and systems use resistance for current control. Ignition primary resistors, also called ballast resistors, maintain and protect the electronic control unit (ECU) from excessive current. The headlamp rheostat adds or subtracts resistance to dim or brighten interior lamps. A carbon pile resistance in the Sun VAT-40 tester "loads" the battery for cranking-voltage and charging system tests. A sliding contact resistance is used on some A/C and heating controls to adjust interior temperature by increasing or decreasing air volume and fan speed. A wire-wound resistor is used on some fuel pumps to reduce pump speed. REDUCE ARCING AND "RFI" Some ignition components use resistance to reduce arcing and radio frequency interference (RFI). Condensers use the high resistance of a dielectric (insulating) material to separate conductive plates that soak up electrostatic charges and current surges that cause RFI and point arcing. Spark plug cables, also called carbon resistance wires, reduce current flow but transmit high voltage to the spark plugs. This causes an extremely hot spark without RFI or rapid burning of the plug electrodes. Spark plugs, themselves, have a carbon core to achieve the same results. SENSE OPERATING CONDITIONS Other components use resistance in sensing and monitoring operating conditions. The resistance added to or subtracted from a sensing circuit changes the current flow which is used for input to a control device, gauge, or actuator. The coolant temperature sensor uses a device that changes resistance with temperature. The fuel-level sensor uses a type of potentiometer, or sliding-contact resistance. The automatic headlamp control uses a photoresistor. The manifold vacuum sensor uses a crystal which changes resistance with pressure. And, with the use of electronic control systems growing rapidly, many more sensors and actuators are using the variation of resistance to operate. ELECTRICAL COMPONENTS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 26. Types Of Resistors Three basic types of resistors are use a m automotive electrical systems ... fixed value, stepped or tapped, and variable. Different symbols are used for the different types of resistors. FIXED-VALUE RESISTORS Two types of fixed-value resistors are used: wire- wound and carbon. Wire-wound resistors are made with coils of resistance wire. Sometimes called power resistors, they are very accurate and heat stable. The resistance value is marked. Carbon resistors are common in Toyota electronic systems. Carbon is mixed with binder; the more carbon, the lower the resistance. Some have the resistance value stamped on, others are rated by wafts of power; most have color-code bands to show the resistance value. Four bands are used ... the first two bands give the resistance digits, the next band is the number of zeros, and the last band gives the "tolerance." A resistor with four bands - red, green, black, and brown from left to right - would be sized as follows: • The first two bands set the digits ... red (2), green (5). • The next band is the number of zeros. Black is "0" zeros. So the resistor has a base value of 25Ω. • And, the last band is the tolerance ... brown (1 %). So, the resistance value is "25 ohms plus or minus .25 ohms" (24.75Ω to 25.25Ω ). ELECTRICAL COMPONENTS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 27. STEPPED OR TAPPED RESISTORS Stepped or tapped resistors have two or more fixed resistance values. The different resistances (carbon or wire) are connected to different terminals in a switch. As the switch is moved, different resistance values are placed in the circuit. A typical Toyota application is in the heater motor's blower-fan switch. VARIABLE RESISTORS Three types of variable resistors are used: rheostats, potentiometers, and thermistors. • RHEOSTAT - Toyota uses a rheostat on the headlamp switch to dim or brighten dash panel lighting. Rheostats have two connections ... one to the fixed end of a resistor, one to a sliding contact on the resistor. Turning the control moves the sliding contact away from or toward the fixed end, increasing or decreasing the resistance. • POTENTIOMETER - Toyota uses a potentiometer in the EFI airflow meter. Potentiometers have three connections ... one at each end of a resistor and one on a sliding contact. Turning the control places more or less resistance in the circuit. • THERMISTOR - Toyota uses NTC (negative temperature coefficient) thermistors in temperature sensors and PTC (positive temperature coefficient) thermistors in the electric assist choke. Both types of thermistors change resistance with increasing temperature (NTC, resistance goes down as temperature goes up; PTC, resistance goes up as temperature go up.) ELECTRICAL COMPONENTS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 28. Controls Control devices used in electrical circuits on Toyota vehicles include a variety of switches, relays, and solenoids. Electronic control devices include capacitors, diodes, and transistors. Controls are needed to start, stop, or redirect current flow. Most switches require physical movement for operation, relays and solenoids are operated with electromagnetism, electronic controls are operated electrically. SWITCHES Switches are the most common circuit control device. They usually have two or more sets of contacts. Opening the contacts is called "opening" or "breaking the circuit," while closing the contacts is called "closing" or "making" the circuit. "Poles" refer to the number of input circuit terminals. "Throws" refer to the number of output circuits. Such switches are referred to as SPST (single- pole, single-throw), SPDT (single-pole, double- throw), and MPMT (multiple-pole, multiple-throw). The various types of switches include: • Hinged pawl - a simple SPST switch to make or break a circuit. • Momentary contact - another SPST switch, normally open or closed, which makes or breaks the circuit when pressed ... typically used for the horn switch. • SPDT - one wire in, two wires out ... commonly used in high-beam / low-beam headlamp circuits. • MPMT - movable contacts are linked to sets of output terminals ... may be used for the transmission neutral start switch. • Mercury switch - liquid mercury flows between contacts to make circuit ... commonly used to turn engine compartment and trunk lamps on and off. • Temperature-sensitive switch - a bimetal element bends when heated to make contact completing a circuit or to break contact opening a circuit. The same principle is also used in time- delay switches and flashers. ELECTRICAL COMPONENTS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 29. RELAYS A relay is simply a remote-control switch, which uses a small amount of current to control a large amount of current. A typical relay has a control circuit and a power circuit. The control circuit is fed current by the power source, and the current flows through a switch and an electromagnetic coil to ground. The power circuit is also fed current from the power source, and the current flows to an armature which can be attracted by the magnetic force on the coil. In operation, when the control circuit switch is open, no current flows to the relay. The coil is not energized, the contacts are open, and no power goes to the load. When the control circuit switch is closed, however, current flows to the relay and energizes the coil. The resulting magnetic field pulls the armature down, closing the contacts and allowing power to the load. Many relays are used on Toyotas for controlling high current in one circuit with low current in another circuit. The relay control circuit can be switched from the power supply side or, more common in Toyotas, from the ground side. SOLENOIDS Solenoids are electromagnetic switches with a movable core that converts current flow into mechanical movement. In a "pulling" type solenoid, the magnetic field pulls a core into a coil. These solenoids are called magnetic switches on Toyota starters. A pull-in coil "pulls" the core into the coil, and a hold-in coil "holds" the core in place. In a "push-pull" type solenoid, a permanent magnet is used for the core. By changing the direction of current flow, the core is "pulled in" or "pushed out." A typical use is on electric door locks. ELECTRICAL COMPONENTS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 30. CAPACITORS Capacitors use an electrostatic field to "soak up" or store an electrical charge. In a circuit, a capacitor will build up a charge on its negative plate. Current flows until the capacitor charge is the same as that of the power source. It will hold this charge until it is discharged through another circuit (such as ground). Always handle capacitors with care; once charged, they can be quite shocking long after the power is removed. • TYPES A capacitor has two conducting plates separated by an insulating material or dielectric. Three types are used: ceramic for electronic circuits, paper and foil for noise suppression in charging and ignition systems, and electrolytic for turn-signal flashers. Different symbols are used for ordinary and electrolytic capacitors. • RATINGS Automotive capacitors are rated in microfarads, and the rating is usually stamped on the case. Always choose a capacitor rated for the maximum expected voltage. • DIAGNOSIS / TESTING Capacitors can be tested for short circuits using an ohmmeter. Connect one test lead to the capacitor mounting clip and the other test lead to the capacitor pigtail connector. The meter needle will first show some continuity as the meter's battery charges the capacitor, then will swing to infinite resistance (∞). If only continuity is seen, the capacitor is most likely shorted. ELECTRICAL COMPONENTS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 31. Electronics "Electronic" devices and systems provide today's vehicles with added comfort, convenience, safety, and performance. These devices and systems, like their "electrical" counterparts, control electricity to do work. The current flows through a semiconductor - rather than through wires. The movement usually produces an electrical signal - rather than heat, light, or motion. And, this signal may be transmitted, amplified, or used in special circuits to perform logical decision-making functions. Since there are seldom any moving (electromechanical) parts, these devices and systems are often called solid-state electronics. SEMICONDUCTORS Semiconductors can act like conductors or insulators. They have a resistance higher than that of conductors like copper or iron, but lower than that of insulators like glass or rubber. They have special electrical properties: • Conductivity can be increased by mixing in certain substances; • Resistance can be changed by light, temperature, or mechanical pressure; and, • Light can be produced by passing current through them. DIODES Diodes are semiconductor devices which act as one way electrical check valves. Diodes will allow current flow in one direction (anode to cathode), but block it in the reverse direction (cathode to anode). • TYPES / USES There are several types of diodes. Rectifying diodes change low-current AC to DC in the charging system. Power rectifiers can handle larger currents in electronic power supplies. Zener diodes can function as voltage sensitive switches. They turn "on" to allow current flow once a certain voltage is reached. They are often used in voltage regulation applications. Light- emitting diodes (LEDs) are used for indicator lights and digital displays. And, photodiodes detect light for sensors. • SYMBOLS Symbols for various diodes are shown. The arrow points in the "forward" direction of current flow (anode to cathode). Zener diodes have a "Z" shaped bar on the cathode side. LEDs and photodiodes are enclosed in a circle with incoming or outgoing light indicated. ELECTRICAL COMPONENTS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 32. Transistors Transistors are semiconductor devices for controlling current flow. A "transistor" (transformer + resistor) transfers signals across the resistance of two semiconductor materials. • TYPES / USES There are many types of transistors. Ordinary or bipolar transistors are most common for switching and amplifying. Power transistors are a variation for larger currents; exposed metal carries away heat. Phototransistors are another variation, used as light-sensitive switches in speedometer and headlamp systems. Field-effect transistors (FETs) are quite different. They are used as switches, amplifiers, and voltage controlled resistors. • SYMBOLS Bipolar transistors are shown with a line and arrow for the emitter, a heavy T-shaped line for the base, and a line without an arrow for the collector. The emitter arrow points to the circuit's negative side. Phototransistors have incoming light arrows added. And, FETs have an arrow showing negative (N) or positive (P) voltage. • OPERATION In bipolar transistors, a small base current (I b) between the emitter-base "turns on" the transistor and causes a larger current (I c) to flow between the emitter-collector. In phototransistors, light striking the base "turns on" the transistor. This switches on a second transistor which amplifies the signal. ELECTRONIC CIRCUITS AND SYSTEMS Individual semiconductor devices are called discrete devices, a number of them may be used in a circuit. Such devices are common in charging, ignition, and headlamp circuits that handle large amounts of power. The more sophisticated electronic control systems now being used on the vehicle, however, make use of integrated circuits and microprocessors or onboard computers. • INTEGRATED CIRCUITS An integrated circuit (IC) has hundreds, even thousands, of discrete devices on a single silicon chip. These include diodes, transistors, resistors, and capacitors. The IC is usually packaged in ceramic or plastic and each tiny device inside is connected to one or more leads that plug into a larger on-vehicle circuit. One type can process analog signals - those that change continuously with time. Another type can process digital signals - those that change intermittently "on" or "off" with time. • MICROPROCESSORS Microprocessors, or on-board computers, are used on various electronic control systems. Such systems have three basic parts: 1) sensors tell what is happening; 2) the microprocessor computes the data and decides what to do; and 3) the actuators or controls respond to change or display the condition. The ECS and ABS are examples of such systems. ELECTRICAL COMPONENTS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 33. Protective Devices Electrical circuits are protected from too much current by fuses, fusible links, and circuit breakers. Such devices will interrupt a circuit to prevent high current from melting conductors and damaging loads. Each of these circuit protection devices is sensitive to current, not voltage, and is rated by current-carrying capacity. They are usually located at, or near, the power source for the circuit being protected. As such, they are usually a good starting point during electrical problem troubleshooting. Remember, though, these devices "blow" or open a circuit because of a problem. Always locate and correct the problem before replacing a fuse or fusible link or resetting a circuit breaker. FUSES Fuses are the most common circuit protection device. Fuses have a fusible element, or low- melting-point metal strip, in a glass tube or plug-in plastic cartridge. These fuses are located in a fuse block under the dash or behind a kick panel. Most circuits - other than the headlamp, starter, and ignition systems - receive power through the fuse block. Battery voltage is supplied to a buss bar in the block. One end of each fuse is connected to this bar, the other end to the circuit it protects. Fuse ratings range from 0.5 to 35 amps, but 7.5 - amp to 20-amp fuses are most common. ELECTRICAL COMPONENTS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 34. FUSIBLE LINKS Some circuits use fusible links, or fuse links, for overload protection. Toyotas can have as many as six fusible links protecting circuits for charging, starting, ignition, and certain accessories. Check the "Power Source" page in the Electrical Wiring Diagram manual for the specific vehicle. A fusible link is a short length of smaller gauge wire installed in a circuit with larger conductors. High current will melt the link before it melts the circuit wiring. Such fuse links have special insulation that blisters or bubbles when the link melts. A melted link must be replaced with one of the same size after the cause of the overload has been identified and the problem corrected. CIRCUIT BREAKERS Circuit breakers are used for protecting circuits temporary overloads may occur and where power must be quickly restored. A bimetal strip is used, similar to that in a temperature-sensitive switch. When heated, the two metals expand differently and cause the strip to bend. The "breaker" is normally closed and it opens when the bimetal element bends. Some circuit breakers are self- resetting, others must be manually reset. Circuit breakers are used on Toyota vehicles to protect circuits for the defogger, heater, air conditioner, power windows, power door locks, and sun roof. ELECTRICAL COMPONENTS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 35. ELECTRICAL COMPONENTS ASSIGNMENT NAME: 1. Describe two power sources used in a vehicle. 2. Explain the term “load” and how it is used in a circuit. 3. Describe the two types of resistors and how each is used. 4. Explain the color code of a resistor that is: “Brown, Orange, Red, Silver. 5. Describe a “stepped resistor “ and how it differs from a “fixed resister”. 6. List and describe three types of “variable resistors”. 7. Explain how a “NTC” thermistor differs from a “PTC” thermistor. 8. List six types of switches used in automobiles. 9. Describe the two circuits used in a relay. 10 Explain how a “relay” differs from a “solenoid”. 11. Explain how current flows into a “capacitor”. 12. Explain the term “semiconductor”. 13. Draw, label, and describe the basic function of a “diode”. 14. Draw, label, and describe the basic function of a “bi-polar transistor”. 15. Explain the term “Integrated Circuit”. 16. List three types of “circuit protective devices”. 17. Describe the basic construction of a “fuse” or “fuse element”. 18. Explain how a “fuse element” differs from a “fusible link”. 19. Describe the basic construction of a “circuit breaker”.
  • 36. ANALOG VS. DIGITAL METERS Ultimately, your diagnosis of vehicle electrical system problems will come down to using a voltmeter, ammeter, or ohmmeter to pinpoint the exact location of the problem. There are two types of each meter—analog and digital. Analog meters use a needle and calibrated scale to indicate values. Digital meters display those values on a digital display. This chapter will help you understand how these meters work as well as the advantages and disadvantages of each. Before using a meter, read the manufacturer's operating instructions. Reading analog meters usually requires simple mental calculations. For example, a meter might have three voltage ranges: 4.0 V, 20 V and 40 V, but only two scales: 4.0 V and 20 V. In order to use the 40 V range, you need to multiply the needle reading on the 4.0 V scale by 10 (or for that matter, the 20 V scale by 2). Digital meters are usually simpler to read and many will adjust to the proper range required for the circuit or device they are connected to. These meters are known as auto-ranging meters. Other digital meters require the operator to select the proper range. In any case it is important to learn the symbols used in a digital readout so you can interpret the reading. The electrical units of measure symbols are: M for mega or million K for kilo or thousand m for milli or one-thousandth u for micro or one-millionth The three types of meters—voltmeters, ammeters and ohmmeters—connect to the circuits or devices in different ways. This is necessary to get accurate measurements and to prevent damage to the meters. VOLTMETERS— ANALOG AND DIGITAL Voltmeters measure voltage or voltage drop in a circuit. Voltage drop can be used to locate excessive resistance in the circuit which could cause poor performance or improper operation. Lack of voltage at a given point may indicate an open circuit or ground. On the other hand, low voltage or high voltage drop, may indicate a high resistance problem like a poor connection. Voltmeters must be connected in parallel with the device or circuit so that the meter can tap off a small amount of current. That is, the positive or red lead is connected to the circuit closest to the positive side of the battery. The negative or black lead is connected to ground or the negative side of the circuit. If a voltmeter is connected in series, its high resistance would reduce circuit current and cause a false reading. ANALOG AND DIGITAL METERS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 37. Because voltmeters are always hooked to a circuit in parallel, they become part of the circuit and reduce the total resistance of the circuit. If a voltmeter has a resistance that is too low in comparison to the circuit, it will give a false measurement. The false reading is due to the meter changing the circuit by lowering the resistance, which increases the current flow in the circuit. The effect a voltmeter has on the circuit to which it is attached is sometimes referred to as "loading effect" of the meter. The loading effect a voltmeter has on a circuit is determined by the total resistance of the circuit in relation to the impedance of the voltmeter. Every voltmeter has an impedance, which is the meter's internal resistance. The impedance of a conventional analog voltmeter is expressed in "ohms per volt." The amount of resistance an analog voltmeter represents to the circuit changes in relation to the scale on which it is placed. Digital voltmeters, on the other hand, have a fixed impedance which does not change from scale to scale and is usually 10 M ohms or more. Impedance is the biggest difference between analog and digital voltmeters. Since most digital voltmeters have 50 times more impedance than analog voltmeters, digital meters are more accurate when measuring voltage in high resistance circuits. For example, if you are using a low impedance (20,000 ohms per volt) analog meter on the 20 volt scale (the voltmeter represents 400,000 ohms resistance to the circuit) to measure voltage drop across a 1,000,000 ohm component in a circuit, two and a half times as much current is flowing through the meter than through the component. You are no longer measuring just that component, but the component plus your meter, giving you a false reading of the actual voltage drop across the component. This situation might lead you to believe the voltage at the component is low or that there is high resistance somewhere in the circuit or that the component is defective when it is just the meter you are using. If you use a digital meter with 10 million ohms of impedance to test the same component, only 1/10 of the current will flow through the meter, which means it has very little effect on the circuit being measured. ANALOG AND DIGITAL METERS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 38. AMMETERS— ANALOG AND DIGITAL Ammeters measure amperage, or current flow, in a circuit, and provide information on current draw as well as circuit continuity. High current flow indicates a short circuit, unintentional ground or a defective component. Some type of defect has lowered the circuit resistance. Low current flow may indicate high resistance or a poor connection in the circuit or a discharged battery. No current indicates an open circuit or loss of power. Ammeters must always be connected in series with the circuit, never in parallel. That is, all the circuit current must flow through the meter. It is connected by attaching the positive lead to the positive or battery side of the circuit, and the negative lead to negative or ground side of the circuit, as shown. CAUTION: These meters have extremely low internal resistance. If connected in parallel, the current running through the parallel branch created by the meter might be high enough to damage the meter along with the circuit the meter is connected to. Also, since all the current will flow through the ammeter when it is connected be sure that the circuit current will not exceed the maximum rating of the meter. There is not a great difference between analog and digital ammeters. Digital meters are often capable of measuring smaller currents, all the way down to microamps. They are easier to use because they give a specific value, eliminating the need to interpret the analog meter's needle on its scale. Generally speaking, most digital ammeters are combined with a voltmeter. OHMMETERS— ANALOG AND DIGITAL An ohmmeter is powered by an internal battery that applies a small voltage to a circuit or component and measures how much current flows through the circuit or component. It then displays the result as resistance. Ohmmeters are used for checking continuity and for measuring the resistance of components. Zero resistance indicates a short while infinite resistance indicates an open in a circuit or device. A reading higher than the specification indicates a faulty component or a high resistance problem such as burnt contacts, corroded terminals or loose connections. ANALOG AND DIGITAL METERS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 39. Ohmmeters, because they are self- powered, must never be connected to a powered circuit as this may blow a fuse in the meter and damage its battery. Unless the circuit being measured contains a diode, polarity (attaching the leads in a particular order) is inconsequential. An analog ohmmeter should be calibrated regularly by connecting the two leads together and zeroing the meter with the adjust knob. This compensates for changes in the state of charge of the internal battery. CAUTION: Analog ohmmeters may apply a higher voltage to a circuit than a digital ohmmeter, causing damage to solid state components. Use analog ohmmeters with care. Digital meters, on the other hand, apply less voltage to a circuit, so damage is less likely. Analog meters can also bias, or turn on, semi-conductors and change the circuit by allowing current to flow to other portions of the circuit. Most digital meters have a low voltage setting which will not bias semi- conductors and a higher voltage setting for testing semiconductors. The information displayed on a digital meter in the diode test function differs from one meter brand to another. Some digital meters will display a value which represents the perceived resistance of the diode in forward bias. Other meters will display the forward bias voltage drop of the diode. Digital ohmmeters do have one limitation. Due to the small amount of current they pass through the device being tested, they cannot check some semiconductors in circuits, such as a clamping diode on a relay coil. Many analog ohmmeters will, when switched to the ohm function, reverse the polarity of the test leads. In other words, the red lead may become negative and the black lead may become positive. The meter will function properly as long as you are aware of this and reverse the leads. This is especially important when working with diodes or transistors which are polarity sensitive and only allow current to flow from the positive to the negative end. To check for polarity reversal, set the ohmmeter in ohm function and connect its leads to the leads of a voltmeter (red to red, black to black). If the voltmeter shows a negative value, that particular ohmmeter reverses polarity in ohm function. Most digital meters do not reverse polarity. You should note that ohmmeters do little good in low resistance, high current- carrying circuits such as starters. They cannot find points of high resistance because they only use a small amount of current from their internal batteries. In a large conductor (such as a battery cable), this current meets little resistance. A voltage drop test during circuit operation is much more effective at locating points of high resistance in this type of circuit. Taken with permission from the Toyota Advanced Electrical Course#672, ANALOG AND DIGITAL METERS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 40. ANALOG AND DIGITALMETERS ASSIGNMENT NAME: 1. Explain how reading an Analog meter differs from a Digital meter. 2. Explain the following electrical units of measure symbols ( M, K, m, u ). 3. List three types of meters. 4. Describe how voltmeters are connected to a circuit. 5. Explain how “meter loading” affects the circuit. 6. Describe “meter impedance” and how it effects a circuit? 7. List the fixed impedance value of a digital voltmeter. 8. Explain how the impedance of a digital meter differs from an analog meter. 9. Describe how ammeters are connected to a circuit. 10. Explain how analog ohmmeters differ from digital ohmmeters in setup. 11. Explain what precautions one should take while connecting an ohmmeter to a circuit.
  • 41. CONDUCTORS Conductors are needed to complete the path for electrical current to flow from the power source to the working devices and back to the power source. POWER OR INSULATED CONDUCTORS Conductors for the power or insulated current path may be solid wire, stranded wire, or printed circuit boards. Solid, thin wire can be used when current is low. Stranded, thick wire is used when current is high. Printed circuitry - copper conductors printed on an insulating material with connectors in place - is used where space is limited, such as behind instrument panels. Special wiring is needed for battery cables and for ignition cables. Battery cables are usually very thick, stranded wires with thick insulation. Ignition cables usually have a conductive carbon core to reduce radio interference. GROUND PATHS Wiring is only half the circuit in Toyota electrical systems. This is called the "power" or insulated side of the circuit. The other half of the path for current flow is the vehicle's engine, frame, and body. This is called the ground side of the circuit. These systems are called single-wire or ground-return systems. A thick, insulated cable connects the battery's positive ( + ) terminal to the vehicle loads. As insulated cable connects the battery's negative ( - ) cable to the engine or frame. An additional grounding cable may be connected between the engine and body or frame. Resistance in the insulated side of each circuit will vary depending on the length of wiring and the number and types of loads. Resistance on the ground side of all circuits must be virtually zero. This is especially important: Ground connections must be secure to complete the circuit. Loose or corroded ground connections will add too much resistance for proper circuit operation. SYSTEM POLARITY System polarity refers to the connections of the positive and negative terminals of the battery to the insulated and ground sides of the electrical system. On Toyota vehicles, the positive (+) battery terminal is connected to the insulated side of the system. This is called a negative ground system having positive polarity. Knowing the polarity is extremely important for proper service. Reversed polarity may damage alternator diodes, cause improper operation of the ignition coil and spark plugs, and may damage other devices such as electronic control units, test meters, and instrument panel gauges. WIRE, TERMINAL AND CONNECTOR REPAIR Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 42. HARNESSES Harnesses are bundles of wires that are grouped together in plastic tubing, wrapped with tape, or molded into a flat strip. The colored insulation of various wires allows circuit tracing. While the harnesses organize and protect wires going to common circuits, don't over look the possibility of a problem inside. WIRE INSULATION Conductors must be insulated with a covering or "jacket." This insulation prevents physical damage, and, more important, keeps the current flow in the wire. Various types of insulation are used depending on the type of conductor. Rubber, plastic, paper, ceramics, and glass are good insulators. CONNECTORS Various types of connectors, terminals, and junction blocks are used on Toyota vehicles. The wiring diagrams identify each type used in a circuit. Connectors make excellent test points because the circuit can be "opened" without need for wire repairs after testing. However, never assume a connection is good simply because the terminals seem connected. Many electrical problems can be traced to loose, corroded, or improper connections. These problems include a missing or bent connector pin. WIRE, TERMINAL AND CONNECTOR REPAIR Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 43. CONNECTOR REPAIR The repair parts now in supply are limited to those connectors having common shapes and terminal cavity numbers. Therefore, when there is no available replacement connector of the same shape or terminal cavity number, please use one of the alternative methods described below. Make sure that the terminals are placed in the original order in the connector cavities, if possible, to aid in future diagnosis. 1 . When a connector with a different number of terminals than the original part is used, select a connector having more terminal cavities than required, and replace both the male and female connector parts. Example: You need a connector with six terminals, but the only replacement available is a connector with eight terminal cavities. Replace both the male and female connector parts with the eight terminal part, transfering the terminals from the old connectors to the new connector. 2. When several different type terminals are used in one connector, select an appropriate male and female connector part for each terminal type used, and replace both male and female connector parts. Example: You need to replace a connector that has two different types of terminals in one connector. Replace the original connector with two new connectors, one connector for one type of terminal, another connector for the other type of terminal. 3. When a different shape of connector is used, first select from available parts a connector with the appropriate number of terminal cavities, and one that uses terminals of the same size as, or larger than, the terminal size in the vehicle. The wire lead on the replacement terminal must also be the same size as, or larger than, the nominal size of the wire in the vehicle. ("Nominal" size may be found by looking at the illustrations in the back of this book or by direct measurement across the diameter of the insulation). Replace all existing terminals with the new terminals, then insert the terminals into the new connector. Example: You need to replace a connector that is round and has six terminal cavities. The only round replacement connector has three terminal cavities. You would select a replacement connector that has six or more terminal cavities and is not round, then select terminals that will fit the new connector. Replace the existing terminals, then insert them into the new connector and join the connector together. WIRE, TERMINAL AND CONNECTOR REPAIR Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 44. CONDUCTOR REPAIR Conductor repairs are sometimes needed because of wire damage caused by electrical faults or by physical abuse. Wires may be damaged electrically by short circuits between wires or from wires to ground. Fusible links may melt from current overloads. Wires may be damaged physically by scraped or cut insulation, chemical or heat exposure, or breaks caused during testing or component repairs. WIRE SIZE Choosing the proper size of wire when making circuit repairs is critical. While choosing wires too thick for the circuit will only make splicing a bit more difficult, choosing wires too thin may limit current flow to unacceptable levels or even result in melted wires. Two size factors must be considered: wire gauge number and wire length. • WIRE GAUGE NUMBER Wire gauge numbers are determined by the conductor's cross-section area. In the American Wire Gauge system, "gauge" numbers are assigned to wires of different thicknesses. While the gauge numbers are not directly comparable to wire diameters and cross- section areas, higher numbers (16, 18, 20) are assigned to increasingly thinner wires and lower numbers (1, 0, 2/0) are assigned to increasingly thicker wires. The chart shows AWG gauge numbers for various thicknesses. Wire cross-section area in the AWG system is measured in circular mils. A mil is a thousandth of an inch (0.001). A circular mil is the area of a circle 1 mil (0.001) in diameter. In the metric system used worldwide, wire sizes are based on the cross-section area in square millimeters (mm 2 ). These are not the same as AWG sizes in circular mils. The chart shows AWG size equivalents for various metric sizes. • WIRE LENGTH Wire length must be considered when repairing circuits because resistance increases with longer lengths. For instance, a 16-gauge wire can carry an 18-amp load for 10 feet without excessive voltage drop. But, if the section of wiring being replaced is only 3-feet long, an 18-gauge wire can be used. Never use a heavier wire than necessary, but - more important - never use a wire that will be too small for the load. WIRE, TERMINAL AND CONNECTOR REPAIR Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 45. WIRE REPAIRS • Cut insulation should be wrapped with tape or covered with heat-shrink tubing. In both cases, overlap the repair about 1/2-inch on either side. • If damaged wire needs replacement, make sure the same or larger size is used. Also, attempt to use the same color. Wire strippers will remove insulation without breaking or nicking the wire strands. • When splicing wires, make sure the battery is disconnected. Clean the wire ends. Crimp and solder them using rosin-core, not acid-core, solder. • SOLDERING Soldering joins two pieces of metal together with a lead and tin alloy. In soldering, the wires should be spliced together with a crimp. The less solder separating the wire strands, the stronger the joint. • SOLDER Solder is a mixture of lead and tin plus traces of other substances. Flux core wire solder (wire solderwith a hollow center filled with flux) is recommended for electrical splices. • SOLDERING FLUX Soldering heats the wires. In so doing, it accelerates oxidization, leaving a thin film of oxide on the wires that tends to reject solder. Flux removes this oxide and prevents further oxidation during the soldering process. Rosin or resin-type flux must be used for all electrical work. The residue will not cause corrosion, nor will it conduct electricity. • SOLDERING IRONS The soldering iron should be the right size for the job. An iron that is too small will require excessive time to heat the work and may never heat it properly. A low- wattage (25-100 W) iron works best for wiring repairs. • CLEANING WORK All traces of paint, rust, grease, and scale must be removed. Good soldering requires clean, tight splices. WIRE, TERMINAL AND CONNECTOR REPAIR Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 46. • TINNING THE IRON The soldering iron tip is made of copper. Through the solvent action of solder and prolonged heating, it will pit and corrode. An oxidized or corroded tip will not satisfactorily transfer heat from the iron to the work. It should be cleaned and tinned. Use a file and dress the tip down to the bare copper. File the surfaces smooth and flat. Then, plug the iron in. When the tip color begins to change to brown and light purple, dip the tip in and out of a can of soldering flux (rosin type). Quickly apply rosin core wire solder to all surfaces. The iron must be at operating temperature to tin properly. When the iron is at the proper temperature, solder will melt quickly and flow freely. Never try to solder until the iron is properly tinned. • SOLDERING WIRE SPLICES Apply the tip flat against the splice. Apply rosin-core wire solder to the flat of the iron where it contacts the splice. As the wire heats, the solder will flow through the splice. • RULES FOR GOOD SOLDERING 1. Clean wires. 2. Wires should be crimped together. 3. Iron must be the right size and must be hot. 4. Iron tip must be tinned. 5. Apply full surface of soldering tip to the splice. 6. Heat wires until solder flows readily. 7. Use rosin-core solder. 8. Apply enough solder to form a secure splice. 9. Do not move splice until solder sets. 10. Place hot iron in a stand or on a protective pad. 11. Unplug iron as soon as you are finished. WIRE, TERMINAL AND CONNECTOR REPAIR Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 47. Step 1. Identify the connector and terminal type. 1. Replacing Terminals a. Identify the connector name, position of the locking clips, the un-locking direction and terminal type from the pictures provided on the charts. Step 2. Remove the terminal from the connector. 1. Disengage the secondary locking device or terminal retainer. a. Locking device must be disengaged before the terminal locking clip can be released and the terminal removed from the connector. b. Use a miniature screwdriver or the terminal pick to unlock the secondary locking device. 2. Determine the primary locking system from the charts. a. Lock located on terminal b. Lock located on connector c. Type of tool needed to unlock d. Method of entry and operation WIRE, TERMINAL AND CONNECTOR REPAIR Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 48. 3. Remove terminal from connector by releasing the locking clip. a. Push the terminal gently into the connector and hold it in this position. b. Insert the terminal pick into the connector in the direction shown in the chart. c. Move the locking clip to the un-lock position and hold it there. NOTE: Do not apply excessive force to the terminal. Do not pry on the terminal with the pick. d. Carefully withdraw the terminal from the connector by pulling the lead toward the rear of the connector. NOTE: Do not use too much force. If the terminal does not come out easily, repeat steps (a.) through (d.). 4. Measure "nominal" size of the wire lead by placing a measuring device, such as a micrometer or Vernier Caliper, across the diameter of the insulation on the lead and taking a reading. 5. Select the correct replacement terminal, with lead, from the repair kit. WIRE, TERMINAL AND CONNECTOR REPAIR Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 49. 6. Cut the old terminal from the harness. a. Use the new wire lead as a guide for proper length. NOTE: If the length of wire removed is not approximately the same length as the new piece, the following problems may develop: Too short - tension on the terminal, splice, or the connector, causing an open circuit. Too long - excessive wire near the connector, may get pinched or abraded, causing a short circuit. NOTE: If the connector is of a waterproof type, the rubber plug may be reused. 7. Strip insulation from wire on the harness and replacement terminal lead. a. Strip length should be approximately 8 to 10 mm (3/8 in.). NOTE: Strip carefully to avoid nicking or cutting any of the strands of wire. NOTE: If heat shrink tube is to be used, it must be installed at this time, sliding it over the end of one wire to be spliced. (See Step 3, 4. B. 1. for instructions on how to use heat shrink tube.) NOTE: If the connector is a waterproof type, the rubber plug should be installed on the terminal end at this time. WIRE, TERMINAL AND CONNECTOR REPAIR Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 50. 1. Select correct size of splice from the repair kit. a. Size is based on the nominal size of the wire (three sizes are available). Part Number Wire Size Small 00204-34130 16-22 AWG 1.0 - 0.2 mm Medium 00204-34137 14-16 AWG 2.0 - 1.0 mm Large 00204-34138 10 - 12 AWG 5.0 - 3.0 mm 2. Crimp the replacement terminal lead to the harness lead. a. Insert the stripped ends of both the replacement lead and the harness lead into the splice, overlapping the wires inside the splice. NOTE: Do not place insulation in the splice, only stripped wire. b. Do not use position marked "INS". The crimping tool has positions marked for insulated splices (marked "INS") that should not be used, as they will not crimp the splice tightly onto the wires. c. Use only position marked "NON INS". 1. With the center of the splice correctly placed between the crimping jaws, squeeze the crimping tool together until the contact points of the crimper come together. NOTE: Make sure the wires and the splice are still in the proper position before closing the crimping tool ends. Use steady pressure in making the crimp. 2. Make certain that the splice is crimped lightly. WIRE, TERMINAL AND CONNECTOR REPAIR Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 51. 3. Solder the completed splice using only rosin core solder. a. Wires and splices must be clean. b. A good mechanical joint must exist, because the solder will not hold the joint together. c. Heat the joint with the soldering iron until the solder melts when pressed onto the joint. d. Slowly press the solder into the hot splice on one end until it flows into the joint and out the other end of the splice. NOTE: Do not use more solder than necessary to achieve a good connection. There should not be a "glob" of solder on the splice. e. When enough solder has been applied, remove the solder from the joint and then remove the soldering iron. 4. Insulate the soldered splice using one of the following methods: a. Silicon tape (provided in the wire repair kit) 1. Cut a piece of tape from the roll approximately 25 mm (1 in.) long. 2. Remove the clear wrapper from the tape. NOTE: The tape will not feel "sticky" on either side. 3. Place one end of the tape on the wire and wrap the tape tightly around the wire. You should cover one-half of the previous wrap each time you make a complete turn around the wire. (When stretched, this tape will adhere to itself.) 4. When completed, the splice should be completely covered with the tape and the tape should stay in place. If both of these conditions are not met, remove the tape and repeat steps 1 through 4. NOTE: If the splice is in the engine compartment or under the floor, or in an area where there might be abrasion on the spliced area, cover the silicon tape with vinyl tape. WIRE, TERMINAL AND CONNECTOR REPAIR Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 52. b. Heat shrink tube (provided in the wire repair kit) 1. Cut a piece of the heat shrink tube that is slightly longer than the splice, and slightly larger in diameter than the splice. 2. Slide the tube over the end of one wire to be spliced. (THIS STEP MUST BE DONE PRIOR TO JOINING THE WIRES TOGETHER!) 3. Center the tube over the soldered splice. 4. Using a source of heat, such as a heat gun, gently heat the tubing until it has shrunk tightly around the splice. NOTE: Do not continue heating the tubing after it has shrunk around the splice. It will only shrink a certain amount, and then stop. It will not continue to shrink as long as you hold heat to it, so be careful not to melt the insulation on the adjoining wires by trying to get the tubing to shrink further. Step 4. Install the terminal into the connector. 1. If reusing a terminal, check that the locking clip is still in good condition and in the proper position. a. If it is on the terminal and not in the proper position, use the terminal pick to gently bend the locking clip back to the original shape. b. Check that the other parts of the terminal are in their original shape. WIRE, TERMINAL AND CONNECTOR REPAIR Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 53. 2. Push the terminal into the connector until you hear a "click". NOTE: Not all terminals will give an audible "click". a. When properly installed, pulling gently on the wire lead will prove the terminal is locked in the connector. 3. Close terminal retainer or secondary locking device. a. If the connector is fitted with a terminal retainer, or a secondary locking device, return it to the lock position. 4. Secure the repaired wire to the harness. a. If the wire is not in the conduit, or secured by other means, wrap vinyl tape around the bundle to keep it together with the other wires. WIRE, TERMINAL AND CONNECTOR REPAIR Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 54. WIRE, TERMINAL AND CONNECTOR REPAIR ASSIGNMENT NAME: 1. Explain which type of wire is used when current flow is high. 2. Explain what is mean by system polarity and how is it used today. 3. Explain how the colors of the wire insulation are used and give an example. 4. Explain how wire is sized, different sizing systems, and provide examples. 5. Name the correct type of solder used for electrical repair repair and why 6. Outline the procedure for “Tinning an Iron”. 7. List the rules for good soldering. 8. Outline in detail the correct procedure for splicing a new wire end on. 9. When and why is a heat gun used?
  • 55. General The battery is the primary "source" of electrical energy on Toyota vehicles. It stores chemicals, not electricity. Two different types of lead in an acid mixture react to produce an electrical pressure. This electrochemical reaction changes chemical energy to electrical energy. Battery Functions 1. ENGINE OFF: Battery energy is used to operate the lighting and accessory systems. 2. ENGINE STARTING: Battery energy is used to operate the starter motor and to provide current for the ignition system during cranking. 3. ENGINE RUNNING: Battery energy may be needed when the vehicle's electrical load requirements exceed the supply from the charging system. In addition, the battery also serves as a voltage stabilizer, or large filter, by absorbing abnormal, transient voltages in the vehicle's electrical system. Without this protection, certain electrical or electronic components could be damaged by these high voltages. Battery Types 1. PRIMARY CELL: The chemical reaction totally destroys one of the metals after a period of time. Small batteries for flashlights and radios are primary cells. 2. SECONDARY CELLS: The metals and acid mixture change as the battery supplies voltage. The metals become similar, the acid strength weakens. This is called discharging. By applying current to the battery in the opposite direction, the battery materials can be restored. This is called charging. Automotive lead-acid batteries are secondary cells. 3. WET-CHARGED: The lead-acid battery is filled with electrolyte and charged when it is built. During storage, a slow chemical reaction will cause self- discharge. Periodic charging is required. For Toyota batteries, this is every 5 to 7 months. 4. DRY-CHARGED: The battery is built, charged, washed and dried, sealed, and shipped without electrolyte. It can be stored for 12 to .18 months. When put into use, it requires adding electrolyte and charging. 5. LOW-MAINTENANCE: Most batteries for Toyota vehicles are considered low-maintenance batteries. Such batteries are built to reduce internal heat and water loss. The addition of water should only be required every 15,000 miles or so. BATTERIES Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 56. Construction 1. CASE: Container which holds and protects all battery components and electrolyte, separates cells, and provides space at the bottom for sediment (active materials washed off plates). Translucent plastic cases allow checking electrolyte level without removing vent caps. 2. COVER: Permanently sealed to the top of the case; provides outlets for terminal posts, vent holes for venting of gases and for battery maintenance (checking electrolyte, adding water). 3. PLATES: Positive and negative plates have a grid framework of antimony and lead alloy. Active material is pasted to the grid ... brown-colored lead dioxide (Pb02) on positive plates, gray- colored sponge lead (Pb) on negative plates. The number and size of the plates determine current capability ... batteries with large plates or many plates produce more current than batteries with small plates or few plates. 4. SEPARATORS: Thin, porous insulators (woven glass or plastic envelopes) are placed between positive and negative plates. They allow passage of electrolyte, yet prevent the plates from touching and shorting out. 5. CELLS: An assembly of connected positive and negative plates with separators in between is called a cell or element. When immersed in electrolyte, a cell produces about 2.1 volts (regardless of the number or size of plates). Battery cells are connected in series, so the number of cells determines the battery voltage. A "1 2 - volt" battery has six cells. 6. CELL CONNECTORS: Heavy, cast alloy metal straps are welded to the negative terminal of one cell and the positive terminal of the adjoining cell until all six cells are connected in series. 7. CELL PARTITIONS: Part of the case, the partitions separate each cell. 8. TERMINAL POSTS: Positive and negative posts (terminals) on the case top have thick, heavy cables connected to them. These cables connect the battery to the vehicle's electrical system (positive) and to ground (negative). 9. VENT CAPS: Types include individual filler plugs, strip-type, or box-type. They allow controlled release of hydrogen gas during charging (vehicle operation). Removed, they permit checking electrolyte and, if necessary, adding water. 10. ELECTROLYTE: A mixture of sulfuric acid (H2SO4) and water (H2O). It reacts chemically with the active materials in the plates to create an electrical pressure (voltage). And, it conducts the electrical current produced by that pressure from plate to plate. A fully charged battery will have about 36% acid and 64% water. BATTERIES Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 57. CELL THEORY A lead-acid cell works by a simple principle: when two different metals are immersed in an acid solution, a chemical reaction creates an electrical pressure. One metal is brown-colored lead dioxide (Pb02). It has a positive electrical charge. The other metal is gray colored sponge lead (Pb). It has a negative electrical charge. The acid solution is a mixture of sulfuric acid (H2SO4) and water (H20). It is called electrolyte. If a conductor and a load are connected between the two metals, current will flow. This discharging will continue until the metals become alike and the acid is used up. The action can be reversed by sending current into the cell in the opposite direction. This charging will continue until the cell materials are restored to their original condition. BATTERIES Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 58. ELECTROCHEMICAL REACTION A lead-acid storage battery can be partially discharged and recharged many times. There are four stages in this discharging/charging cycle. 1. CHARGED: A fully charged battery contains a negative plate of sponge lead (Pb), a positive plate of lead dioxide (Pb02), and electrolyte of sulfuric acid (H2SO4) and water (H20). 2. DISCHARGING: As the battery is discharging, the electrolyte becomes diluted and the plates become sulfated. The electrolyte divides into hydrogen (H2) and sulfate(S04) . The hydrogen (H2) combines with oxygen (0) from the positive plate to form more water (H20). The sulfate combines with the lead (Pb) in both plates to form lead sulfate (PbS04) 3. DISCHARGED: In a fully discharged battery, both plates are covered with lead sulfate (PbSO4) and the electrolyte is diluted to mostly water (H2O). 4. CHARGING: During charging, the chemical action is reversed. Sulfate (S04) leaves the plates and combines with hydrogen (H2) to become sulfuric acid (H2SO4). Free oxygen (02) combines with lead (Pb) on the positive plate to form lead dioxide (Pb02). Gassing occurs as the battery nears full charge, and hydrogen bubbles out at the negative plates, oxygen at the positive. BATTERIES Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 59. Capacity Ratings The battery must be capable of cranking the engine and providing adequate reserve capacity. Its capacity is the amount of electrical energy the battery can deliver when fully charged. Capacity is determined by the size and number of plates, the number of cells, and the strength and volume of electrolyte. The most commonly used ratings are: • Cold Cranking Amperes (CCA) • Reserve Capacity (RC) • Amp-Hours (AH) • Power (Watts) COLD-CRANKING AMPERES (CCA) The battery's primary function is to provide energy to crank the engine during starting. This requires a large discharge in a short time. The CCA Rating specifies, in amperes, the discharge load a fully charged battery at 0˚F (-1 7.8˚C) can deliver for 30 seconds while maintaining a voltage of at least 1.2 volts per cell (7.2 volts total for a 12-volt battery). Batteries used on various Toyota vehicles have CCA ratings ranging from 350 to 560 amps. RESERVE CAPACITY (RC) The battery must provide emergency energy for ignition, lights, and accessories if the vehicle's charging system fails. This requires adequate capacity at normal temperatures for a certain amount of time. The RC Rating specifies, in minutes, the length of time a fully charged battery at 80˚F (26.7'C) can be discharged at 25 amps while maintaining a voltage of at least 1.75 volts per cell (10.5 volts total for a 12-volt battery). Batteries used on various Toyota vehicles have RC ratings ranging from 55 to 115 minutes. AMP-HOURS (AH) The battery must maintain active materials on its plates and adequate lasting power under light-load conditions. This method of rating batteries is also called the 20-hour discharge rating. Original equipment batteries are rated in amp-hours. The ratings of these batteries are listed in the parts microfiche. The Amp-Hour Rating specifies, in amphours, the current the battery can provide for 20 hours at 80˚F (26.7˚C) while maintaining a voltage of at least 1.75 volts per cell (10.5 volts total for a 12- volt battery). For example, a battery that can deliver 4 amps for 20 hours is rated at 80 amp-hours (4 x 20 = 80). Batteries used on various Toyota vehicles have AH ratings ranging from 40 to 80 amp-hours. POWER (WATTS) The battery's available cranking power may also be measured in watts. The Power Rating, in watts, is determined by multiplying the current available by the battery voltage at 0˚F (-1 7.8˚C). Batteries used on various Toyota vehicles have power ratings ranging from 2000 to 4000 watts. BATTERIES Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 60. FACTORS AFFECTING CHARGING Five factors affect battery charging by increasing its internal resistance and CEMF (counter-electromotive force produced by the electrochemical reaction): 1. TEMPERATURE: As the temperature decreases the electrolyte resists charging. A cold battery will take more time to charge; a warm battery, less time. Never attempt to charge a frozen battery. 2. STATE-OF-CHARGE: The condition of the battery's active materials will affect charging. A battery that is severely discharged will have hard sulfate crystals on its plates. The vehicle's charging system may charge at too high of a rate to remove such sulfates. 3. PLATE AREA: Small plates are charged faster than large plates. When sulfation covers most of the plate area, the charging system may not be able to restore the battery. 4. IMPURITIES: Dirt and other impurities in the electrolyte increase charging difficulty. 5. GASSING: Hydrogen and oxygen bubbles form at the plates during charging. As these bubble out, they wash away active material, cause water loss, and increase charging difficulty. BATTERIES Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 61. BATTERIES Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 62. Diagnosis and Testing All batteries require routine maintenance to identify and correct problems caused by physical abuse and low electrolyte levels. A visual inspection can identify such physical problems. A state-of-charge test checks the electrolyte strength. And, electrical testing identifies overcharging or undercharging problems. These tests include a capacity, or heavy- load, test. SAFETY FIRST! When testing or servicing a battery, safety should be your first consideration. The electrolyte contains sulfuric acid. It can eat your clothes. It can burn your skin. It can blind you if it gets in your eyes. It can also ruin a car's finish or upholstery. If electrolyte is splashed on your skin or in your eyes, wash it away immediately with large amounts of water. If electrolyte is spilled on the car, wash it away with a solution of baking soda and water. When a battery is being charged, either by the charging system or by a separate charger, gassing will occur. Hydrogen gas is explosive. Any flame or spark can ignite it. If the flame travels into the cells, the battery may explode. Safety precautions include: • Wear gloves and safety glasses. • Remove rings, watches, other jewelry. • Never use spark-producing tools near a battery. • Never lay tools on the battery. • When removing cables, always remove the ground cable first. • When connecting cables, always connect the ground cable last. • Do not use the battery ground terminal when checking for ignition spark. • Be careful not to get electrolyte in your eyes or on your skin, the car finish, or your clothing. • If you have to mix battery electrolyte, pour the acid into the water - not the water into the acid. • Always follow the recommended procedures for battery testing and charging and for jump starting an engine. CARE OF ELECTRONICS Disconnecting the battery will erase the memory on electronic devices. Write down trouble codes and programmed settings before disconnecting the battery. Also, to prevent damage to electronic components: • Never disconnect the battery with the ignition ON. • Never use an electric welder without the battery cables disconnected. • Never reverse battery polarity. BATTERIES Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 63. VISUAL INSPECTION Battery service should begin with a thorough visual inspection. This may reveal simple, easily corrected problems, or problems that might require battery replacement. 1 . Check for cracks in the battery case and for broken terminals. Either may allow electrolyte leakage. The battery must be replaced. 2. Check for cracked or broken cables or connections. Replace, as needed. 3. Check for corrosion on terminals and dirt or acid on the case top. Clean the terminals and case top with a mixture of water and baking soda or ammonia. A wire brush is needed for heavy corrosion on the terminals. 4. Check for a loose battery hold-down and loose cable connections. Tighten, as needed. 5. Check the level of electrolyte. The level can be viewed through the translucent plastic case or by removing the vent caps and looking directly into each cell. The proper level is 1/2" above the separators. If necessary, add distilled water to each low cell. Avoid overfilling. When water is added, always charge the battery to make sure the water and acid mix. 6. Check for cloudy or discolored electrolyte caused by overcharging or vibration. This could cause high self discharge. The problem should be corrected and the battery replaced. 7. Check the condition of plates and separators. Plates should alternate dark (+) and light (-). If all are light, severe undercharging is indicated. Cracked separators may allow shorts. The battery should be replaced. An undercharging problem should be corrected. BATTERIES Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 64. 8. Check the tension and condition of the alternator drive belt. A loose belt must be tightened. It will prevent proper charging. A belt too tight will reduce alternator life. It should be loosened to specs. A frayed or glazed belt will fail during operation. Replace it. NOTE: Approved Equipment tension gauge: Nippondenso, BTG-20 (SST) Borroughs BT-33-73F 9. Check for battery drain or parasitic loads using an ammeter. Connect the ammeter in series between the battery negative terminal and ground cable connector. Toyota vehicles typically show less than .020 amp of current to maintain electronic memories ... a reading of more than .035 amp is unacceptable. If the ammeter reads more than .035 amp, locate and correct the cause of excessive battery drain. 10. Check for battery discharge across the top of the battery using a voltmeter. Select the low voltage scale on the meter, connect the negative (black) test lead to the battery's negative post, and connect the positive (red) test lead to the top of the battery case. If the meter reading is more than 0.5 volt, clean the case top using a solution of baking soda and water. BATTERIES Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 65. STATE-OF-CHARGE TEST The state-of-charge test checks the battery's chemical condition. One method uses a hydrometer to measure the specific gravity of the electrolyte. Another method uses a digital voltmeter to check the battery's open circuit voltage and, for a general indication of the battery's condition, check the indicator eye (if the battery has one) or check the headlamp brightness during starting. Specific Gravity Specific gravity means exact weight. The hydrometer compares the exact weight of electrolyte with that of water. Strong electrolyte in a charged battery is heavier than weak electrolyte in a discharged battery. By weight, the electrolyte in a fully charged battery is about 36% acid and 64% water. The specific gravity of water is 1.000. The acid is 1.835 times heavier than water, so its specific gravity is 1.835. The electrolyte mixture of water and acid has a specific gravity of 1.270 is usually stated as "twelve and seventy." By measuring the specific gravity of the electrolyte, you can tell if the battery is fully charged, requires charging, or must be replaced. It can tell you if the battery is charged enough for the capacity, or heavy- load test. TEST PROCEDURE: The following steps outline a typical procedure for performing a state-of-charge test: 1 . Remove vent caps or covers from the battery cells. 2. Squeeze the hydrometer bulb and insert the pickup tube into the cell closest to the battery's positive (+) terminal. 3. Slowly release the bulb to draw in only enough electrolyte to cause the float to rise. Do not remove the tube from the cell. 4. Read the specific gravity indicated on the float. Be sure the float is drifting free, not in contact with the sides of top of the barrel. Bend down to read the hydrometer a eye level. Disregard the slight curvature of liquid on the float. 5. Read the temperature of the electrolyte. 6. Record your readings and repeat the procedure for the remaining cells. TEMPERATURE CORRECTION: The specific gravity changes with temperature. Heat thins the liquid, and lowers the specific gravity. Cold thickens the liquid, and raises the specific gravity. Hydrometers are accurate at 80-F (26.7˚C). If the electrolyte is at any other temperature, the hydrometer readings must be adjusted. Most hydrometers have a built-in thermometer and conversion chart. Refer to the temperature correction chart. For each 1 O˚F (5.5˚C) above 80˚F (26.7˚C), ADD 0.004 to your reading. BATTERIES Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 66. TEST RESULTS: Specific gravity readings tell a lot about battery condition. 1. A fully charged battery will have specific gravity readings around 1.265. 2. Specific gravity readings below 1.225 usually mean the battery is run down and must be charged. 3. Readings around 1.190 indicate that sulfation is about to begin. The battery must be charged. 4. Readings of 1.155 indicate severe discharge. Slow charging is required to restore active materials. 5. Readings of 1.120 or less indicate that the battery is completely discharged. It may require replacement, but slow charging may restore some batteries in this condition. 6. A difference of 50 points (0.050) or more between one or more cells indicates a defective battery. It should be replaced. 7. When the specific gravity of all cells is above 1.225 and the variation between cells is less than 50 points, the battery can be tested under load. Open-Circuit Voltage An accurate digital voltmeter is used to check the battery's open-circuit voltage: 1 . If the battery has just been charged, turn on the headlamps for one minute to remove any surface charge. 2. Turn headlamps off and connect the voltmeter across the battery terminals. 3. Read the voltmeter. A fully charged battery will have an open-circuit voltage of at least 12.6 volts. A dead battery will have an open-circuit voltage of less than 12.0 volts. Indicator Eye Toyota original-equipment batteries have an indicator eye for electrolyte level and specific gravity. If the eye shows red, the electrolyte level is low or the battery is severely discharged. If some blue is showing, the level is okay and the battery is at least 25% charged. NOTE: The indicator eye should be used only as a general indication of electrolyte level and strength. BATTERIES Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 67. HEAVY-LOAD TEST While an open circuit voltage test determines the battery's state of charge, it does not measure the battery's ability to deliver adequate cranking power. A capacity, or heavy-load, test does. A Sun VAT-40 tester is used. If another type of tester is used, follow the manufacturer's recommended procedure. The following steps outline a typical procedure for load testing a battery: 1. Test the open circuit voltage. The battery must be at least half charged. If the open circuit voltage is less than 12.4v, charge the battery. 2. Disconnect the battery cables, ground cable first. 3. Prepare the tester: • Rotate the Load Increase control to OFF. • Check each meter's mechanical zero. Adjust, if necessary. • Connect the tester Load Leads to the battery terminals; RED to positive, BLACK to negative. • Set Volt Selector to INT 18V. Tester voltmeter should indicate battery open-circuit voltage. NOTE: Battery open-circuit voltage should be at least 12.4 volts (75% charged). If not, the battery requires charging. • Set Test Selector to #2 CHARGING. • Adjust ammeter to read ZERO using the electrical Zero Adjust control. 4. Connect the clamp-on Amps Pickup around either tester load cable (disregard polarity). 5. Set the Test Selector Switch to #1 STARTING. 6. Load the battery by turning the Load Increase control until the ammeter reads 3 times the amp- hour (AH) rating or one-half the cold-cranking ampere (CCA) rating. 7. Maintain the load for no more than 15 seconds and note the voltmeter reading. 8. Immediately turn the Load Increase control OFF. 9. If the voltmeter reading was 10.0 volts or more, the battery is good. If the reading is 9.6 to 9.9 volts, the battery is serviceable, but requires further testing. Charge and re-test. If the reading was below 9.6 volts, the battery is either discharged or defective. NOTE: Test results will vary with temperature. Low temperatures will reduce the reading. The battery should be at operating temperature. BATTERIES Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 68. Battery Service Battery service procedures include charging, cleaning, jump starting, and replacement. Follow the recommended procedures. CHARGING A battery in good condition may occasionally fail to crank the engine fast enough to make it start. In such cases, the battery may require charging. All battery chargers operate on the same principle: an electric current is applied to the battery to reverse the chemical action in the cells. Never connect or disconnect leads with the charger turned ON. Follow the battery charger manufacturer's instructions. And, do not attempt to charge a battery with frozen electrolyte. When using a battery charger, always disconnect the battery ground cable first. This will minimize the possibility of damage to the alternator or to electronic components. Otherwise, use a charger with polarity protection that prevents reverse charging. The battery can be considered fully charged when all cells are gassing freely and when there is no change in specific gravity readings for more than one hour. BATTERIES Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 69. Fast Charging Fast charging is used to charge the battery for a short period of time with a high rate of current. Fast charging may shorten battery life. If time allows, slow charging is preferred. Some low maintenance batteries cannot be fast charged. 1. Preparation for charging. • Clean dirt, dust, or corrosion off the battery; if necessary, clean the terminals. • Check the electrolyte level and add distilled water if needed. • If the battery is to be charged while on the vehicle, be sure to disconnect both (-) (+) terminals. 2. Determine the charging current and time for fast charging. • Some chargers have a test device for determining the charging current and required time. • If the charger does not have a test device, refer to the chart below to determine current and time. 3. Using the charger: • Make sure that the main switch and timer switch are OFF and the current adjust switch is at the minimum position. • Connect the positive lead of the charger to the battery positive terminal (+) and the negative lead of the charger to the battery negative terminal (-). • Connect the charger's power cable to the electric outlet. • Set the voltage switch to the correct battery voltage. • Set the main switch at ON. • Set the timer to the desired time and adjust the charging current to the predetermined amperage. 4. After the timer is "off," check the charged condition using a voltmeter. • Correct Voltage: 12.6 volts or higher. If the voltage does not increase, or if gas is not emitted no matter how long the battery is charged, there may be a problem with the battery, such as an internal short. 5. When the voltage reaches the proper reading: • Set the current adjust switch to minimum. • Turn off the main switch of the charger. • Disconnect the charger cables from the battery terminals. • Wash the battery case to clean off the acid emitted. Slow Charging High charging rates are not good for completely charging a battery. To completely charge a battery, slow charging with a low current is required. Slow charging procedures are the same as those for fast charging, except for the following: 1. The maximum charging current should be less than 1 1/10th of the battery capacity. For instance, a 40 AH battery should be slow charged at 4 amps or less. 2. Set the charger switch to the slow position (if provided). 3. Readjust the current control switch from time to time while charging. 4. As the battery gets near full charge, hydrogen gas is emitted. When there is no further rise in battery voltage for more than one hour, the battery is completely charged. • Battery Voltage: 12.6 volts or higher BATTERIES Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 70. CLEANING Cleaning the battery will aid your visual inspection and reduce the possibility of current leakage. The battery case can be cleaned with a brush and diluted ammonia or soda solution. Avoid getting the solution in the cells. The battery terminals and cable connections can be cleaned with the cleaning tool (brush) made for that purpose. Remove all corrosion and oxidation, both common causes of high resistance. JUMP STARTING When jump starting a dead battery with a booster battery, proper connections prevent sparks. First, connect the two positive terminals. Then, connect one end of the jumper cable to the negative terminal of the booster battery. And, connect the other end to a good ground away from the dead battery. If a spark occurs, it won't be near the battery. BATTERY REPLACEMENT If a battery requires replacement: use a cable puller to remove terminal clamps; unfasten the battery hold- down; lift the battery from its carrier with the proper tool; wash and paint corroded parts; replace any damaged parts of the hold-down, support tray, or cables; and select and install a battery of the proper size and capacity rating. Taken with permission from the Toyota Basic Electrical Course #622, BATTERIES Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 71. SELF TEST This brief self-test will help you measure your understanding of The Battery. The style is the same as that used for A.S.E. certification tests. The answers to this self test are shown on next page. 1. The amount of current a battery can produce is controlled by the: A. plate thickness B. plate surface area C. strength of acid D. discharge of load 2. How many volts are produced in each cell of a battery? A. 2.1 B. 6. 0 C. 9.6 D. 12.0 3. The plates of a discharged battery are: A. two similar metals in the presence of an electrolyte B. two similar metals in the presence of water C. two dissimilar metals in the presence of an electrolyte D. two dissimilar metals in the presence of water 4. A battery's reserve capacity is measured in: A. amperes B. wafts C. amp-Hours D. minutes 5. Severe battery undercharging is indicated if: A. active materials are washed off the plates B. the terminals are corroded C. the plates (+ and -) are both very light colored D. the electrolyte is cloudy 6. To check for battery drain, you would connect an ammeter between the: A. battery and alternator B. battery and (-) terminals C. battery terminal and ground cable D. battery terminal and ground cable 7. What is the state of charge of a battery that has a specific gravity of 1.190 at 80˚F (26.7'C)? A. Completely discharged B. About 1/2 charged C. About 3/4 charged D. Fully charged 8. A battery heavy-load test discharges the battery for: A. 5 seconds B. 10 seconds C. 15 seconds D. 20 seconds 9. When performing a battery capacity test on a 12-volt battery, the voltage should not fall below: A. 12.0 volts B. 10.6 volts C. 9.6 volts D. 8.6 volts 10. The preferred method of recharging a "dead" battery is: A. fast charging B. slow charging C. cycling the battery D. with a VAT-40 BATTERIES Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 72. SELF-TEST ANSWERS For the preceding self-test on The Battery, the following best complete the sentence or answer the question. In cases where you may disagree with the choice - or may simply want to reinforce your understanding - please review the appropriate workbook page or pages noted. 1 . "B" - The number and size of the plates determine current capability. (Page 2.) 2. "A" - When immersed in electrolyte, a cell produces about 2.1 volts (regardless of the number of size of plates). (Page 2.) 3. "B" - In a fully discharged battery, both plates are covered with lead sulfate and the electrolyte is diluted to mostly water. (Page 4.) 4. "D" - The Reserve Capacity rating is the length of time, in minutes, a fully charged battery at 80'F (26.70C) can be discharged at 25 amps while maintaining a voltage of at least 1.75 volts per cell. (Page 5.) 5. "C" - Plates should alternate dark (+) and light It all are light, severe undercharging is indicated. (Page 9.) 6. "D" - Check for battery drain using an ammeter between the battery negative terminal and ground cable connector. (Page 10.) 7. "B" - Specific gravity readings around 1.190 indicate that sulfation is about to begin. The battery is about 50% charged, and requires charging. (Page 12.) 8. "C" - In a battery load test, maintain the load for no more than 15 seconds and note the voltmeter reading. (Page 13.) 9. "C" - In a battery capacity or heavy-load test, if the voltmeter reading falls below 9.6 volts, the battery is either discharged or defective. (Page 13.) 10. "B" - Slow charging is preferred. (Page 15.) BATTERIES Page 18 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 73. BATTERIES ASSIGNMENT NAME: 1. Describe the basic construction of a lead-acid battery. 2. Explain what materials are used to make up the: positive plate, negative plate, and electrolyte. 3. Describe the basic chemical operation of a single cell that makes a battery. 4. List the voltage output of both a single battery cell and a six cell automotive battery. Be exact. 5. Explain the four basic battery “capacity ratings” systems. 6. List the gases that are produced during the charging process from both the positive and the negative plates. 7. Explain why repeated “overcharging” or “cycling” is harmful to a battery. 8. List the three basic battery tests / inspections that can be performed. 9. List ten (10) items inspected while performing a “visual inspection”. 10. Explain the terms “battery drain” and “parasitic loads”. 11. Describe the procedure of checking parasitic drain on a car. 12. List the maximum parasitic drain allowed. 13. Describe why and how baking soda is used on an automotive battery. 14. List two methods of checking a battery’s “state of charge. 15. List the specific gravity readings of a battery that has the following states of charge: 100%, 50%, 0%. 16. Explain the term “specific gravity” and how it is measured. 17. List the open circuit voltages of a battery with the following states of charge 100%, 50%, 0%. 18. Describe the “open circuit voltage” test procedure. 19. What is the minimum charge a battery needs to perform a Heavy Load Test. 20. Explain in detail the “Heavy Load” or “Capacity” test procedure. 21. What is the maximum time a Heavy Load Test should be performed? 22 How much of a load is placed on a battery that has a 500 CCA rating? 23. What action should be taken if battery voltage drops to 8.7 volts during a heavy load test? What if the voltage was 10.3 volts?
  • 74. General Starting the engine is possibly the most important function of the vehicle's electrical system. The starting system performs this function by changing electrical energy from the battery to mechanical energy in the starting motor. This motor then transfers the mechanical energy, through gears, to the flywheel on the engine's crankshaft. During cranking, the flywheel rotates and the air-fuel mixture is drawn into the cylinders, compressed, and ignited to start the engine. Most engines require a cranking speed of about 200 rpm. Toyota Starting Systems Two different starting systems are used on Toyota vehicles. Both systems have two separate electrical circuits ... a control circuit and a motor circuit. One has a conventional starting motor. This system is used on most older-model Toyotas. The other has a gear reduction starting motor. This system is used on most current Toyotas. A heavy-duty magnetic switch, or solenoid, turns the motor on and off. It is part of both the motor circuit and the control circuit. Both systems are controlled by the ignition switch and protected by a fusible link. On some models, a starter relay is used in the starter control circuit. On models with automatic transmission, a neutral start switch prevents starting with the transmission in gear. On models with manual transmission, a clutch switch prevents starting unless the clutch is fully depressed. On 4WD Truck and 4-Runner models, a safety cancel switch allows starting on hills without the clutch depressed. It does so by establishing an alternate path to ground. TOYOTA STARTING SYSTEMS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 75. Starting System Operation TOYOTA STARTING SYSTEMS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 76. Starting Motor Construction GENERAL The starter motors used on Toyota vehicles have a magnetic switch that shifts a rotating gear (pinion gear) into and out of mesh with the ring gear on the engine flywheel. Two types of motors are used: conventional and gear reduction. Both are rated by power output in kilowatts (KW) ... the greater the output, the greater the cranking power. CONVENTIONAL STARTER MOTOR The conventional starter motor contains the components shown. The pinion gear is on the same shaft as the motor armature and rotates at the same speed. A plunger in the magnetic switch (solenoid) is connected to a shift lever. When activated by the plunger, the shift lever pushes the pinion gear and causes it to mesh with the flywheel ring gear. When the engine starts, an over-running clutch disengages the pinion gear to prevent engine torque from ruining the starting motor. This type of starter was used on most 1975 and older Toyota vehicles. It is currently used on certain Tercel models. Typical output ratings are 0.8, 0.9, and 1.0KW. In most cases, replacement starters for these older motors are gear-reduction motors. TOYOTA STARTING SYSTEMS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 77. GEAR-REDUCTION STARTER MOTOR The gear-reduction starter motor contains the components shown. This type of starter has a compact, high-speed motor and a set of reduction gears. While the motor is smaller and weighs less than conventional starting motors, it operates at higher speed. The reduction gears transfer this torque to the pinion gear at 1/4 to 1/3 the motor speed. The pinion gear still rotates faster than the gear on a conventional starter and with much greater torque (cranking power). The reduction gear is mounted on the same shaft as the pinion gear. And, unlike in the conventional starter, the magnetic switch plunger acts directly on the pinion gear (not through a drive lever) to push the gear into mesh with the ring gear. This type of starter was first used on the 1973 Corona MKII with the 4M, six cylinder engine. It is now used on most 1975 and newer Toyotas. Ratings range from 0.8KW on most Tercels and some older models to as high as 2.5KW on the diesel Corolla, Camry and Truck. The cold-weather package calls for a 1.4KW or 1.6KW starter, while a 1.0KW starter is common on other models. The gear-reduction starter is the replacement starter for most conventional starters. TOYOTA STARTING SYSTEMS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 78. Starting Motor Operation CONVENTIONAL STARTER MOTOR IGNITION SWITCH IN "ST" • Current flows from the battery through terminal "50" to the hold-in and pull-in coils. Then, from the pull-in coil, current flows through terminal "C" to the field coils and armature coils. • Voltage drop across the pull-in coil limits the current to the motor, keeping its speed low. • The solenoid plunger pulls the drive lever to mesh the pinion gear with the ring gear. • The screw spline and low motor speed help the gears mesh smoothly. PINION AND RING GEARS ENGAGED • When the gears are meshed, the contact plate on the plunger turns on the main switch by closing the connection between terminals "30" and "C." • More current goes to the motor and it rotates with greater torque (cranking power). • Current no longer flows in the pull-in coil. The plunger is held in position by the hold-in coil's magnetic force. IGNITION SWITCH IN "ON" • Current no longer flows to terminal "50," but the main switch remains closed to allow current flow from terminal "C" through the pull-in coil to the hold-in coil. • The magnetic fields in the two coils cancel each other, and the plunger is pulled back by the return spring. • The high current to the motor is cut off and the pinion gear disengages from the ring gear. • A spring-loaded brake stops the armature. TOYOTA STARTING SYSTEMS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 79. GEAR-REDUCTION STARTER MOTOR IGNITION SWITCH IN "ST" • Current flows from the battery through terminal "50" to the hold-in and pull-in coils. Then, from the pull-in coil, current flows through terminal "C" to the field coils and armature coils. • Voltage drop across the pull-in coil limits the current to the motor, keeping its speed low. • The magnetic switch plunger pushes the pinion gear to mesh with the ring gear. • he screw and low motor speed help the gears mesh smoothly. PINION AND RING GEARS ENGAGED • When the gears are meshed, the contact plate on he plunger turns on the main switch by closing the connection between terminals "30" and "C." • More current goes to the motor and it rotates with greater torque. • Current no longer flows in the pull-in coil. The plunger is held in position by the hold-in coil's magnetic force. IGNITION SWITCH IN "ON" • Current no longer flows to terminal "50," but the main switch remains closed to allow current flow from terminal "C" through the pull-in coil to the hold-in coil. • The magnetic fields in the two coils cancel each other, and the plunger is pulled back by the return spring. • The high current to the motor is cut off and the pinion gear disengages from the ring gear. • The armature has less inertia than the one in a conventional starter. Friction stops it, so a brake is not needed. TOYOTA STARTING SYSTEMS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 80. OVER-RUNNING CLUTCH Both types of starter motors used on Toyota starting systems have a one-way clutch, or over- running clutch. This clutch prevents damage to the starter motor once the engine has been started. It does so, by disengaging its housing (which rotates with the motor armature) from an inner race which is combined with the pinion gear. Spring loaded wedged rollers are used. Without an over-running clutch, the starter motor would be quickly destroyed if engine torque was transferred through the pinion gear to the armature. TOYOTA STARTING SYSTEMS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 81. Diagnosis and Testing The starting system requires little maintenance. Simply, keep the battery fully charged and all electrical connections clean and tight. Diagnosis of starting system problems is relatively easy. The system combines electrical and mechanical components. The cause of a starting problem may be electrical (e.g., faulty switch) or mechanical (e.g., wrong engine oil or a faulty flywheel ring gear). Specific symptoms of starting system problems include: • The engine will not crank; • The engine cranks slowly; • The starter keeps running; • The starter spins, but the engine will not crank; and, • The starter does not engage or disengage properly. For each of these problems, refer to the chart below for the possible causes and needed actions. Diagnosis starts with a thorough visual inspection. Testing includes: a starter motor current draw test, starter circuit voltage drop tests, operational and continuity checks of control components, and starter motor bench tests. TOYOTA STARTING SYSTEMS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 82. VISUAL INSPECTION A visual inspection of the starting system can uncover a number of simple, easy-to-correct problems. • SAFETY FIRST: The same safety considerations used in checking the battery apply here. Remove rings, wristwatch, other jewelry that might contact battery terminals. Wear safety glasses and protective clothing. Be careful not to spill electrolyte and know what to do if electrolyte gets in your eyes, on your skin or clothing, or on the car's finish. Write down programmed settings on electronic components. Avoid causing sparks. • STARTING PERFORMANCE: Check the starting performance. Problem symptoms, possible causes, and needed actions are shown in the chart on the previous page. • BATTERY CHECKS: Inspect the battery for corrosion, loose connections. Check the electrolyte level, condition of the plates and separators, and state of charge (specific gravity or open-circuit voltage). Load test the battery. It must be capable of providing at least 9.6 volts during cranking. STARTER CABLES: Check the cable condition and connections. Insulation should not be worn or damaged. Connections should be clean and tight. STARTER CONTROL CIRCUIT: Check the operation of the ignition switch. Current should be supplied to the magnetic switch when the ignition is "on" and the clutch switch or neutral start switch is closed. Faulty parts that prevent cranking can be located using a remote-control starter switch and a jumper wire. Use the "split half" diagnosis method. Ohmmeter checks can also identify component problems. TOYOTA STARTING SYSTEMS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 83. CURRENT DRAW TEST A starter current draw test provides a quick check of the entire starting system. With the Sun VAT-40 tester, it also checks battery's cranking voltage. If another type of tester is used, follow the manufacturer's recommended procedure. The starting current draw and cranking voltage should meet the specifications listed for the Toyota model being tested. Typical current draw specs are 130-150 amps for 4-cylinder models and 175 amps for 6-cylinder models. Cranking voltage specs range from 9.6 to 11 volts. Always refer to the correct repair manual. Only perform the test with the engine at operating temperature. The following steps outline a typical procedure for performing a current draw test on a starting system: 1. This test should be made only with a serviceable battery. The specific gravity readings at 800˚F should average at least 1. 190 (50% charged). Charge the battery, if necessary. 2. Prepare the tester: • Rotate the Load Increase control to OFF. • Check each meter's mechanical zero. Adjust, if necessary. • Connect the tester Load Leads to the battery terminals; RED to positive, BLACK to negative. NOTE: Battery open-circuit voltage should be at least 12.2 volts (50% charged). If not, the battery requires charging. • Set Volt Selector to INT 18V. Tester voltmeter should indicate battery open-circuit voltage. • Set Test Selector to #2 CHARGING. • Adjust ammeter to read ZERO using the electrical Zero Adjust control. 3. Connect the clamp-on Amps Pickup around the battery ground cable or cables. 4. Make sure all lights and accessories are off and vehicle doors are closed. 5. Set the Test Selector switch to #1 STARTING. 6. Disable the ignition so the engine does not start during testing. 7. Crank the engine, while observing the tester ammeter and voltmeter. • Cranking speed should be normal (200-250 rpm). • Current draw should not exceed the maximum specified. • Cranking voltage should be at or above the minimum specified. 8. Restore the engine to starting condition and remove tester leads. TEST RESULTS: High current draw and low cranking speed usually indicate a faulty starter. High current draw may also be caused by engine problems. A low cranking speed with low current draw, but high cranking voltage, usually indicates excessive resistance in the starter circuit. Remember that the battery must be fully charged and its connections tight to insure accurate results. TOYOTA STARTING SYSTEMS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 84. VOLTAGE-DROP TESTS Voltage-drop testing can detect excessive resistance in the starting system. High resistance in the starter motor circuit (power side or ground side) will reduce current to the starting motor. This can cause slow cranking speed and hard starting. High resistance in the starter control circuit will reduce current to the magnetic switch. This can cause improper operation or no operation at all. A Sun VAT-40 tester or separate voltmeter can be used. The following steps outline a typical procedure for performing voltage-drop tests on the starting system: Motor Circuit (insulated Side) 1. If using the Sun VAT-40, set the Volt Selector to EXT 3V. For other voltmeters, use a low scale. 2. Connect the voltmeter leads ... RED to the battery positive (+) terminal, BLACK to terminal "C" on the starter motor magnetic switch. 3. Disable the ignition so the engine cannot start during testing. NOTE: On models with the Integrated Ignition Assembly, disconnect the "IIA" plug. On others, disconnect the power plug to the remote igniter assembly (black-orange wire). 4. Crank the engine and observe the voltmeter. Less than 0.5 volt indicates acceptable resistance. More than 0.5 volt indicates excessive resistance. This could be caused by a damaged cable, poor connections, or a defective magnetic switch. 5. If excessive resistance is indicated, locate the cause. Acceptable voltage drops are 0.3 volt across the magnetic switch, 0.2 volts for the cable, and zero volts for the cable connection. Repair or replace components, as needed. TOYOTA STARTING SYSTEMS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 85. Motor Circuit (Ground Side) 1. Connect the voltmeter leads ... RED to the starter motor housing, BLACK to the battery ground (-) terminal. 2. Crank the engine and observe the voltmeter. Less than 0.2 volt indicates acceptable resistance. More than 0.2 volt indicates excessive resistance. This could be caused by a loose motor mount, a bad battery ground, or a loose connection. Repair or replace components as necessary. Make sure engine-to-body ground straps are secure. Control Circuit 1. Connect the voltmeter leads ... RED to the battery positive (+) terminal, BLACK to terminal "50" of the starting motor. 2. On vehicles with automatic transmission, place the lever in Park or Neutral. On vehicles with manual transmission, depress the clutch. (NOTE: A jumper wire could be used to bypass either of these switches). 3. Crank the engine and observe the voltmeter. Less than .5 volt is acceptable. If the current draw was high or cranking speed slow, the starter motor is defective. More than .5 volt indicates excessive resistance. Isolate the trouble and correct the cause. 4. Check the neutral start switch or clutch switch for excessive voltage drop. Also check the ignition switch. Adjust or replace a defective switch, as necessary. 5. An alternate method to checking the voltage drop across each component is to leave the voltmeter connected to the battery (+) terminal and move the voltmeter negative lead back through the circuit toward the battery. The point of high resistance is found between the point where voltage drop fell within specs and the point last checked. TOYOTA STARTING SYSTEMS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 86. COMPONENT TESTS For the various tests on starting system components, refer to the appropriate Toyota repair manual for testing procedures and specifications. Ignition Switch and Key The ignition switch should be checked both mechanically as well as electrically. Make sure the switch turns smoothly, without binding. And, check the ignition key for wear or metal chips that might cause the switch to stick in the "start" position. Some duplicate keys have caused this problem. If an electrical problem is suspected, disconnect the battery and check the switch for proper operation and continuity using an ohmmeter. Starter Relay • Continuity Check: Using an ohmmeter, check for continuity between terminals 1 and 3, and, for no continuity, between terminals 2 and 4. Replace the relay if continuity is not as specified. • Operational Check: Apply battery voltage across terminals 1 and 3 and check for continuity between terminals 2 and 4. Replace the relay if operation is not as specified. Neutral Start Switch If the engine will start with the shift selector in any range other than "N" or "P," adjust the switch. First, loosen the switch bolt and set the selector to "N." Then, disconnect the switch connector and connect an ohmmeter between terminals 2 and 3. Adjust the switch until there is continuity. (Refer to appropriate Service Manual for specific vehicle procedures.) TOYOTA STARTING SYSTEMS Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 87. Clutch Start Switch Follow the procedure given in Toyota repair manuals for checking pedal height and freeplay. Then, check the switch for proper operation and continuity. Using an ohmmeter on the switch connector, there should be continuity when the switch is ON (clutch depressed) and no continuity when the switch is OFF (clutch not depressed). If continuity is not as specified, replace the switch. Safety Cancel Switch • Continuity Checks: Using an ohmmeter, there should be no continuity between terminals 2 and 1, 3 and 1, or 2 and 3. If there is continuity, replace the switch. • Operational Checks: Connect a battery between terminals 3 and 1 as shown. No continuity should be seen between terminals 1 and 2. But, when the switch is pushed "on," there should be continuity. If operation is not as specified, replace the safety cancel switch. TOYOTA STARTING SYSTEMS Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 88. TOYOTA STARTING SYSTEMS Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 89. SELF TEST This brief self-test will help you measure your understanding of The Starting System. The style is the same as that used for A.S.E. certification tests. The answers to this self test are shown on next page. 1. The starting system has two circuits. They are the: A. motor circuit and ignition circuit B. insulated circuit and power circuit C. motor circuit and control circuit D. ground circuit and control circuit 2. A basic starter control circuit energizes the magnetic switch through the ignition switch and the: A. solenoid B. neutral start switch C. starter clutch D. regulator 3. On a Toyota gear-reduction starter, the plunger in the magnetic switch: A. pulls a drive lever to mesh the gears B. pushes the pinion gear into mesh with the ring gear C. is held in place by the pull-in coil D. disengages the pinion gear from the starter armature 4. When an engine starts, the pinion gear is disconnected from the starter by the: A. magnetic switch B. plunger C. over-running clutch D. switch return spring 5. If the engine cranks too slow to start, the problem may be caused by: A. engine problems B. a faulty neutral start switch C. an open relay in the control circuit D. a damaged pinion gear 6. If a starter motor spins but does not engage and crank the engine, the problem is most likely caused by a bad: A. magnetic switch B. over-running clutch C. positive battery cable D. ignition switch 7. When performing a starter current draw test, low current draw usually indicates: A. high resistance B. a bad starter C. a discharged battery D. a short in the starter 8. When performing a starter current draw test, high current draw usually indicates: A. a discharged battery B. high resistance C. battery terminal corrosion D. engine problems or a bad starter 9. A test of a starting system reveals that the voltage drop between the battery positive (+) post and the starter motor terminal "C" is about one volt. The most probable cause is: A. low resistance in the motor circuit B. high resistance in the motor circuit C. low resistance in the control circuit D. high resistance in the control circuit 10. The voltage drop on the ground side of the starter motor circuit should be no more than: A. battery voltage B. 0.1 volt C. 0.2 volt D. 0.5 volt TOYOTA STARTING SYSTEMS Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 90. SELF-TEST ANSWERS For the preceding self-test on The Starting System, the following best complete the sentence or answer the question. In cases where you may disagree with the choice - or may simply want to reinforce your understanding - please review the appropriate workbook page or pages noted. 1 . "C" - The starting system has two separate electrical circuits ... a control circuit and a motor circuit. (Page 1.) 2. "B" - If the transmission is in gear, the control circuit between the ignition switch and starter magnetic switch is interrupted by the neutral start switch. (Page 2.) 3. "B" - Unlike in the conventional starter, the magnetic switch plunger acts directly on the pinion gear (not through a drive lever) to push the gear into mesh with the ring gear. (Page 4.) 4. "C" - An over-running clutch disengages the pinion gear and prevents damage to the starter motor when the engine starts. (Page 7.) 5. "A" - If the engine cranks too slow to start, the cause may be a discharged battery, loose or corroded connections, a faulty starter, or engine problems such as the wrong oil. (Page 8.) 6. "B" - If the starter motor spins, but the engine will not crank, check the over-running clutch. (Page 8.) 7. "A" - Low current draw, with a low cranking speed and high cranking voltage, usually indicates excessive resistance in the starting circuit. (Page 10.) 8. "D" - High current draw, with a low cranking speed, usually indicates a faulty starter or engine problems such as the wrong oil or ignition timing. (Page 10.) 9. "B" - With the voltmeter leads connected between the battery (+) terminal and the motor "C" terminal, a reading of more than 0.5 volt indicates excessive resistance (in the motor circuit). (Page 11.) 10. "C" - With the voltmeter leads connected between the battery (-) terminal and the motor housing, a reading of more than 0.2 volt indicates excessive resistance (in the motor ground circuit). (Page 12.) TOYOTA STARTING SYSTEMS Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 91. TOYOTA STARTING SYSTEMS ASSIGNMENT NAME: 1. List the two staring system circuits. 2. List the components that make up the “control circuit”. 3. List the components that make up the “motor circuit”. 4. Explain in detail how a “Conventional Starter” differs from that of a “Gear Reduction Starter”. 5. Explain why an “overrunning clutch” is needed and how it works. 6. Explain how the “starter drive pinion” engages (pushed out) with the ring gear when the ignition key is turned to the “Start” position. 7. List and describe the five items included in a “Visual Inspection”. 8. Explain in detail the steps taken in order to perform a “Current Draw Test”. 9. Explain the procedure and the need for a voltage drop test of the “Motor Circuit”
  • 92. General The charging system converts mechanical energy into electrical energy when the engine is running. This energy is needed to operate the loads in the vehicle's electrical system. When the charging system's output is greater than that needed by the vehicle, it sends current into the battery to maintain the battery's state of charge. Proper diagnosis of charging system problems requires a thorough understanding of the system components and their operation. Operation When the engine is running, battery power energizes the charging system and engine power drives it. The charging system then generates electricity for the vehicle's electrical systems. At low speeds with some electrical loads "on" (e.g., lights and window defogger), some battery current may still be needed. But, at high speeds, the charging system supplies all the current needed by the vehicle. Once those needs are taken care of, the charging system then sends current into the battery to restore its charge. CHARGING SYSTEMS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 93. Toyota Charging Systems Typical charging system components include: IGNITION SWITCH When the ignition switch is in the ON position, battery current energizes the alternator. ALTERNATOR Mechanical energy is transferred from the engine to the alternator by a grooved drive belt on a pulley arrangement. Through electromagnetic induction, the alternator changes this mechanical energy into electrical energy. The alternating current generated is converted into direct current by the rectifier, a set of diodes which allow current to pass in only one direction. VOLTAGE REGULATOR Without a regulator, the alternator will always operate at its highest output. This may damage certain components and overcharge the battery. The regulator controls the alternator output to prevent overcharging or undercharging. On older models, this is a separate electromechanical component which uses a coil and contact points to open and close the circuit to the alternator. On most models today, this is a built-in electronic device. BATTERY The battery supplies current to energize the alternator. During charging, the battery changes electrical energy from the alternator into chemical energy. The battery's active materials are restored. The battery also acts as a "shock absorber" or voltage stabilizer in the system to prevent damage to sensitive components in the vehicle's electrical system. INDICATOR The charging indicator device most commonly used on Toyotas is a simple ON/OFF warning lamp. It is normally off. It lights when the ignition is turned "on" for a check of the lamp circuit. And, it lights when the engine is running if the charging system is undercharging. A voltmeter is used on current Supra and Celica models to indicate system voltage ... it is connected in parallel with the battery. An ammeter in series with the battery was used on older Toyotas. FUSING A fusible link as well as separate fuses are used to protect circuits in the charging system. CHARGING SYSTEMS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 94. Alternator Construction GENERAL Two different types of alternators are used on Toyota vehicles. A conventional alternator and separate voltage regulator were used on all Toyotas prior to 1979. A new compact, high-speed alternator with a built-in IC regulator is now used on most models. Both types of alternators are rated according to current output. Typical ratings range from 40 amps to 80 amps. CONVENTIONAL ALTERNATOR This type of alternator is currently used on some 1986 Tercel models, and all Toyotas prior to 1979. CHARGING SYSTEMS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 95. TOYOTA COMPACT, HIGH-SPEED ALTERNATOR Beginning with the 1983 Camry, a compact, high- speed alternator with a built-in IC regulator is used on Toyota vehicles. Corolla models with the 4A-C engine use a different alternator with an integral IC regulator. This new alternator is compact and lightweight. It provides better performance, as well as improved warning functions. If either the regulator sensor (terminal "S") or the alternator output (terminal "B") become disconnected, the warning lamp goes on. It also provides better serviceability. The rectifier, brush holder, and IC regulator are bolted onto the end frame. CHARGING SYSTEMS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 96. Alternator Terminals Toyota's high-speed alternator has the following terminals: "B", "IG", "S", "U', and "17". When the ignition switch is "on," battery current is supplied to the regulator through a wire connected between the switch and terminal "IG". When the alternator is charging, the charging current flows through a large wire connected between terminal "B" and the battery. At the same time, battery voltage is monitored for the MIC regulator through terminal "S". The regulator will increase or decrease rotor field strength as needed. The indicator lamp circuit is connected through terminal "U'. If there is no output, the lamp will be lit. The rotor field coil is connected to terminal "P, which is accessible for testing purposes through a hole in the alternator end frame. Regulator While engine speeds and electrical loads change, the alternator's output must remain even - not too much, nor too little. The regulator controls alternator output by increasing or decreasing the strength of the rotor's magnetic field. It does so, by controlling the amount of current from the battery to the rotor's field coil. The electromechanical regulator does its job with a magnetic coil and set of contact points. The IC regulator does its job with diodes, transistors, and other electronic components. CHARGING SYSTEMS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 97. Alternator Operation GENERAL The operation of the Toyota compact, high-speed alternator is shown in the following circuit diagrams. IGNITION ON, ENGINE STOPPED CHARGING SYSTEMS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 98. CHARGING SYSTEMS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 99. CHARGING SYSTEMS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 100. Diagnosis and Testing The charging system requires periodic inspection and service. Specific problem symptoms, their possible cause, and the service required are listed in the chart below. The service actions require a thorough visual inspection. Problems identified must be corrected before proceeding with electrical tests. These electrical tests include: an alternator output test, charging circuit voltage- drop tests, a voltage regulator (non-IC) test, charging circuit relay (lamp, ignition, engine) tests, and alternator bench tests. PRECAUTIONS • Make sure battery cables are connected to correct terminals. • Always disconnect battery cables (negative first!) when the battery is given a quick charge. • Never operate an alternator on an open circuit (battery cables disconnected). • Always follow specs for engine speed when grounding terminal "F to bypass the regulator. High speeds may cause excess output that could damage components. • Never ground alternator output terminal "B." It has battery voltage present at all times, even with the engine off. • Do not perform continuity tests with a high- voltage insulation resistance tester. This type of ohmmeter could damage the alternator diodes. CHARGING SYSTEMS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 101. VISUAL INSPECTION A visual inspection should always be your first step in checking the charging system. A number of problems that would reduce charging performance can be identified and corrected. CHECK THE BATTERY • Check for proper electrolyte level and state of charge. When fully charged, specific gravity should be between 1.25 and 1.27 at 80˚F (26.7˚C). • Check the battery terminals and cables. The terminals should be free of corrosion and the cable connections tight. CHECK THE FUSES AND FUSIBLE LINK • Check the fuses for continuity. These include the Engine fuse (10A), Charge fuse (7.5A), and Ignition fuse (7.5A). • Check the fusible link for continuity. INSPECT THE DRIVE BELT • Check for belt separation, cracks, fraying, or glazing. If necessary, replace the drive belt. • Check the drive belt tension using the proper tension gauge, Nippondenso BTG-20 Refer to the appropriate repair manual for proper drive belt tension. "New" belts (used less than 5 minutes on a running engine) are installed with greater tension than "used" belts. Tension specs are different for different models. INSPECT THE ALTERNATOR • Check the wiring and connections. Replace any damaged wires, tighten any loose connections. • Check for abnormal noises. Squealing may indicate drive belt or bearing problems. Defective diodes can produce a whine or hissing noise because of a pulsating magnetic field and vibration. CHECK THE WARNING LAMP CIRCUIT • With the engine warm and all accessories off, turn the ignition to ON. The warning lamp should light. • With the engine started and the ignition in RUN, the warning lamp should be off. • If the lamp does not operate as specified, check the bulb and check the lamp circuit. CHARGING SYSTEMS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 102. ALTERNATOR OUTPUT TEST The alternator output test checks the ability of the alternator to deliver its rated output of voltage and current. This test should be performed whenever an overcharging or undercharging problem is suspected. Output current and voltage should meet the specifications of the alternator. If not, the alternator or regulator (IC or external) may require replacement. A Sun VAT-40 tester, similar testers, or a separate voltmeter and ammeter can be used. Toyota repair manuals detail the testing procedures with an ammeter and voltmeter. Follow the manufacturer's instructions when using special testers, although most are operated similarly. The following steps outline a typical procedure for performing the alternator output test using a Sun VAT-40: CHARGING SYSTEMS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 103. Charging Without Load 1. Prepare the tester: • Rotate the Load Increase control to OFF, • Check each meter's mechanical zero. Adjust, if necessary. • Connect the tester Load Leads to the battery terminals; RED to positive, BLACK to negative. • Set Volt Selector to INT 18V. • Set Test Selector to #2 CHARGING. • Adjust ammeter to read ZERO using the electrical Zero Adjust control. • Connect the clamp-on Amps Pickup around the battery ground (-) cables. 2. Turn the ignition switch to "ON" (engine not running) and read the amount of discharge on the ammeter. This is a base reading for current the alternator must supply for ignition and accessories before it can provide current to charge the battery. NOTE: The reading should be about six amps. 3. Start the engine and adjust the speed to about 2000 rpm. Some models may require a different speed setting. 4. After about 3-4 minutes, read the ammeter and voltmeter. Add this ammeter reading and the reading found in step 2 (engine not running). NOTE: The total current should be less than 10 amps. If it is more, the alternator may still be charging the battery. Once the battery is fully charged, you should get specified results. The voltage should be within the specs for the alternator. This is usually between 13 and 15 volts. Refer to the appropriate repair manual. If the voltage is more than specified, replace the regulator. If the voltage is less than specified, ground the alternator field terminal "F" and check the voltmeter reading. This bypasses the regulator, so do not exceed the specified test speed. If the reading is still less than specified, check the alternator. 5. Remove ground from terminal "F." Charging With Load 6. With the engine running at specified speed, adjust the Load Increase control to obtain the highest ammeter reading possible without causing the voltage to drop lower than 12 volts. 7. Read the ammeter. NOTE: The reading should be within 10% of the alternator's rated output. If it is less, the alternator requires further testing or replacement. CHARGING SYSTEMS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 104. CHARGING SYSTEMS Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 105. VOLTAGE-DROP TESTS Voltage-drop testing can detect excessive resistance in the charging system. These tests determine the voltage drop in the alternator output circuit. Both sides of the circuit should be checked ... insulated side as well as ground side. Excessive voltage drop caused by high resistance in either of these circuits will reduce the available charging current. Under heavy electrical loads, the battery will discharge. A Sun VAT-40 tester or a separate voltmeter can be used. The following steps outline a typical procedure for performing voltage-drop tests using a voltmeter: Output Circuit - Insulated Side 1. Connect the voltmeter positive lead to the alternator's output terminal "B" and the voltmeter's negative lead to the battery's positive (+) terminal. 2. Start the engine and adjust the speed to approximately 2000 rpm. 3. Read the voltmeter. The voltage drop should be less than 0.2 volt. If it is more, locate and correct the cause of the high resistance. Output Circuit - Ground Side 1. Connect the voltmeter's negative lead to the alternator's frame and the voltmeter's positive lead to the battery's negative (-) terminal. 2. Start the engine and run at specified speed (about 2000 rpm). 3. Read the voltmeter. The voltage drop should be 0.2 volt or less. If it is more, locate and correct the cause of high resistance. Excessive resistance is most likely caused by loose or corroded connections. CHARGING SYSTEMS Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 106. CHARGING CIRCUIT RELAY TESTS Various charging system layouts are used on Toyota vehicles. The indicator lamp circuit may or may not be controlled by a relay. Depending on the model, when a relay is used, it may be a separate lamp relay, the ignition main relay, or the engine main relay. Each is checked using an ohmmeter. Charge Lamp Relay When used, the charge lamp relay is located on the right cowl side of the vehicle. The following steps are used to check this relay: 1. Check relay continuity. • Connect the ohmmeter positive (+) lead to terminal "4," the negative (-) lead to terminal "3." Continuity (no resistance) should be indicated. • Reverse the polarity of the ohmmeter leads. No continuity (infinite resistance) should be indicated. • Connect the ohmmeter leads between terminals 1 and "2." No continuity (infinite resistance) should be indicated. If the relay continuity is not as specified, replace the relay. 2. Check relay operation. • Apply battery voltage across terminals "3" and "4." NOTE: Make sure polarity is as shown. • Connect the ohmmeter leads between terminals “1” and "2." Continuity (no resistance) should be indicated. If relay operation is not as specified, replace the relay. CHARGING SYSTEMS Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 107. Ignition Main Relay The ignition main relay is located in the relay box under the instrument panel. The following steps are used to check this relay: 1. Check relay continuity. • Connect the ohmmeter leads between terminals “1” and "3." Continuity (no resistance) should be indicated. • Connect the ohmmeter leads between terminals "2" and "4." No continuity (infinite resistance) should be indicated. If relay continuity is not as specified, replace the relay. 2. Check relay operation. • Apply battery voltage across terminals "l " and "3." • Connect the ohmmeter leads between terminals "2" and 'A." Continuity (no resistance) should be indicated. If relay operation is not as specified, replace the relay. CHARGING SYSTEMS Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 108. ALTERNATOR BENCH TESTS If the on-vehicle checks have indicated that the alternator is defective, it should be removed for bench testing and replacement. Specific procedures for removal, disassembly, inspection, and assembly are noted in the appropriate repair manuals. Only the electrical bench tests are covered here. • Always disconnect the battery ground (-) cable before removing the alternator. • Refer to the appropriate repair manual for test specifications. An ohmmeter is used for electrical bench tests on the rotor, stator, and diode rectifier. The following steps are typical: Rotor Tests • Check the rotor for an open circuit by measuring for resistance between the slip rings. Some resistance (less than 5 ohms) indicates continuity. If there is no continuity (infinite resistance), replace the rotor. • Check the rotor for grounded circuits by measuring for resistance between the rotor and slip ring. Any amount of resistance indicates a ground (continuity). The resistance should be infinite ( 0 ohms ). If not, replace the rotor. CHARGING SYSTEMS Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 109. Diode Tests Diodes can be checked with the alternator on the vehicle using a scope. Scope testing can identify open or shorted diodes, as well as problems in the stator coils. The scope patterns shown below include: a) Normal alternator output; b) one diode short-circuited; c) two diodes of the same polarity short-circuited; d) one diode open; e) two diodes open; f) one phase of the stator coil short-circuited; g) one phase of the stator coil disconnected; and, h) two phases of the stator coil short-circuited. CHARGING SYSTEMS Page 18 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 110. CHARGING SYSTEMS Page 19 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 111. This brief self-test will help you measure your understanding of The Charging System. The style is the same as that used for A.S.E. certification tests. Each incomplete statement or question is followed by four suggested completions or answers. In each case, select the one that best completes the sentence or answers the question. 1. A regulator controls alternator output voltage by regulating: A. sine-wave voltage B. battery voltage C. field current D. output current 2. In an alternator, alternating current is converted to direct current by the: A. stator B. brushes C. rectifier D. regulator 3. If the charging system indicator lamp goes on with the engine running, the cause may be loss of voltage at terminal: A. "IG" B. "S" C. "L" D. "F 4. With the engine not running and the ignition ON, the charge lamp should light. If it doesn't, this may indicate a: A. burned out bulb B. grounded bulb C. loose drive belt D. overcharged battery 5. Which alternator terminal can be grounded for test purposes? A. "B" B. "IG" C. “S" D. "F 6. When performing a visual inspection of the charging system, the alternator drive belt should be checked for proper tension. Technician "A" says that new-belt tension specs are higher than those for used belts. Technician "B" says that the belt tension is different for different Toyota models. Who is right? A. Only A B. Only B C. Both A and B D. Neither A nor B 7. The amount of current the alternator must supply or ignition and accessories is about: A. four amps B. six amps C. eight amps D. ten amps 8. In an alternator output test under load, the output should be: A. about 10 amps B. about 30 amps C. within 10% of rated output D. within 20% of rated output 9. To check for excessive voltage drop on the insulated side of the alternator's output circuit, you would connect a voltmeter between the: A. battery terminal and ignition switch B. battery terminal and ground C. battery terminal and alternator "S" terminal D. battery terminal and alternator "B" terminal 10. High resistance in an alternator output circuit is often caused by: A. a discharged battery B. a shorted diode C. loose or corroded connections D. a bad regulator CHARGING SYSTEMS Page 20 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 112. SELF-TEST ANSWERS For the preceding self-test on The Charging System, the following best complete the sentence or answer the question. In cases where you may disagree with the choice - or may simply want to reinforce your understanding - please review the appropriate workbook page or pages noted. 1 . "C" - The regulator controls alternator output by increasing or decreasing the amount of current from the battery to the rotor field coil. (Page 5.) 2. "C" - The alternating current is changed into direct current by the rectifier, a set of diodes which allow current to pass in only one direction. (Page 2.) 3. "B" - If either the regulator sensor (terminal "S") or the alternator output (terminal "B") become disconnected, the warning lamp goes on. (Page 4.) 4. "A" - If the warning lamp does not light, with the ignition ON and the engine not running, the possible causes include a blown fuse, burned out lamp, loose connections, or faulty relay or regulator. (Page 9.) 5. "D" - Terminal "F is the only terminal that can be grounded. Never ground alternator output terminal "B. It has battery voltage present at all times, even with the engine off. (Page 9.) 6. "C" - A "new belt" is one that has been used for less than 5 minutes. It is installed with more tension than a used belt, because it will stretch some during use. Methods of checking are different for different models. (Page 10.) 7. "B" -The reading should be about six amps. This is the amount of current the alternator must supply for ignition and accessories. (Page 12.) 8. "C" - With the alternator operating at maximum output, the reading should be within 10% of rated output. (Page 12.) 9. "ID" - To check for the insulated circuit voltage drop, connect the voltmeter leads to the battery's (+) terminal and the alternator output (B) terminal. (Page 14.) 10. "C" - Excessive resistance is most likely caused by loose or corroded connections. (Page 14.) CHARGING SYSTEMS Page 21 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved. Taken with permission from the Toyota Basic Electrical Course#622,
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  • 163. SEMICONDUCTORS One of the basic building blocks of all modern electronic devices is the semiconductor. Semiconductors can conduct or block electrical current. Because of this ability, semiconductors serve an important function in everything from relays to the integrated circuits of computers. This chapter examines diodes as well as some of the other components used to construct electronic devices, such as capacitors and resistors. Diodes allow current to flow through them in only one direction and are used in a variety of ways, including suppression of voltage spikes ("de-spiking") and converting alternating current to direct current in an alternator. Capacitors store electrical charges and are used for electrical noise and voltage spike suppression. Capacitors are also used in timer circuits to delay turning on or off a device or system. This chapter will examine each of the following areas: Capacitors Current Flow Theory Semiconductor Theory Diodes CAPACITORS Capacitors have the ability to absorb and store an electrical charge and then release it into the circuit. Capacitors are frequently used in timers which will keep a circuit or device in operation for a period of time after the circuit has been shut off. An example of this is a dome light circuit that stays on for a specified length of time after the door has been closed. A capacitor is constructed from two conducting plates separated by an insulating material called a dielectric. This insulating material can be paper, plastic, film mica, glass, ceramic, air or a vacuum. The plates can be aluminum discs, aluminum foil or a thin film of metal applied to opposite sides of a solid dielectric. These layered materials are either rolled into a cylinder or left flat. The operation of a capacitor is relatively simple. When the capacitor is placed in a circuit, a charge builds on the plates until the plates are at the same potential as the power source. When the source potential is removed, the capacitor will discharge and cause a current to flow in the circuit. If the potential of the source changes, the capacitor will either charge or discharge to match the source, thereby smoothing voltage fluctuations in the circuit. SEMICONDUCTORS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 164. Since current can flow into a capacitor only until the charge reaches the potential of the source, a capacitor will block current in a DC circuit. AC currents are not blocked by a capacitor because the polarity of the AC circuit is continually changing. The unit of measure of capacitance is the "farad." Most capacitors are much less than one farad, and are rated in micro- farads or picofarads. When capacitors are connected in series their total capacitance is reduced, like resistors connected in parallel. When capacitors are connected in parallel their total capacitance increases, like total resistance when resistors are connected in series. There are three types of capacitors: ceramic for electronic circuits, paper and foil for noise suppression in charging and ignition systems, and electrolytic as used in turn signal flashers. Ordinary and electrolytic capacitors are designated by different symbols in wiring diagrams. As stated, capacitors have three uses: Noise suppression—Noise in an audio system is often caused by AC electrical voltage riding on top of the DC voltage supplying power to a radio or tape player. A capacitor connected to the circuit will filter out the AC voltage by allowing it to pass to ground. Most alternators on Toyota vehicles have a capacitor built in for this purpose. Spike suppression—A capacitor can absorb voltage spikes in a circuit. This application has been used in conventional ignition systems to prevent an arc from jumping the breaker points when they are opened. Timers—A resistor put in series with a capacitor can keep current flowing in a circuit for a specified amount of time after power from the source has been removed. This can be used to keep dome lights on after the vehicle doors are closed. The resistor-capacitor or RC circuit in the example above is used to keep a transistor turned on, so the transistor allows current to remain flowing to the system. SEMICONDUCTORS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 165. CURRENT FLOW THEORY Before we discuss semiconductors and how they operate, it is important to understand current flow theory. There are two different theories of how current flows: electron current flow and conventional current flow (sometimes referred to as "hole flow"). The electron current flow theory says that current flow in a circuit is the movement of electrons through the conductors. Since the electrons have a negative charge and unlike charges attract each other, the electrons move from the negative terminal of the battery to the positive terminal. So the electron theory says that current flows from negative to positive. The conventional current flow theory, which has been accepted for many years, says that current flows from the positive terminal of the battery to the negative terminal. The conventional current flow theory is sometimes called the hole flow theory because this theory says that when an electron moves, an empty hole is left behind. The holes are said to travel in the opposite direction from the electrons in the conductor. To understand how this could work think of a line of cars stopped at a stop sign. As one car pulls away from the stop sign a hole is left and the next car in line moves forward to fill the hole. Now the hole has moved back to where the second car was and the third car moves forward to fill it. As each car in turn moves forward to fill the hole, the hole moves to the rear. The cars move one direction and the holes move the other, just like electrons and holes in a circuit. When looking at an electrical circuit, either the electron current flow theory or conventional current flow theory can be applied because the circuit operation and the schematic will be the same. When dealing with diagrams that use electronic symbols, such as diodes and transistors, the arrow in the symbol always points in the direction of conventional current flow. Because the conventional current flow theory is widely accepted in the automotive industry, it is used throughout this book. SEMICONDUCTORS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 166. BASIC THEORY OF SEMICONDUCTOR OPERATION Semiconductors are important to understand because they play such a prominent part in automotive electronics. You will deal with them nearly every time you diagnose a Toyota electronic system. Some materials conduct electrical current better than others. This is due to the number of electrons in the outermost ring, or shell, of electrons of the atoms that make up the materials. The outer shell is called the valence shell" or "ring." If the valence ring has five to eight electrons, it takes a large amount of force to cause one of the electrons to break free from the atom, making that material a poor conductor. Such materials are often used as insulators to block current. materials that are made up of atoms with one to three electrons in their valence ring are good conductors because a small force will cause the electrons to break free. Semiconductors fall somewhere in the middle. Since they have four electrons in their valence rings, they are not good insulators or conductors. Semiconductors are usually made from germanium or silicon which, in their natural states, are pure crystals. Neither have enough free electrons to support significant current flow, but by adding atoms from other materials—a process called doping— the crystals will conduct electricity in a way that is useful in electronic circuits. The semiconductor material, after it has been doped, becomes either N-type material or P-type material. SEMICONDUCTORS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 167. Silicon is the most commonly used semiconductor material. The outer shell of a silicon atom contains four electrons, but it needs eight to be stable. Therefore, the atoms link together to share electrons. In this state, silicon will not conduct current. When silicon is doped with a material such as phosphorous, which has five electrons, the resultant material contains free electrons—known as carriers—and therefore conducts electricity. This creates N-type material, named for its negative charge caused by the excess of electrons. Silicon can also be doped with a material that has fewer than four electrons in its outer shells, as is the case with boron and its three electrons. The resultant structure has "holes" left by the missing electrons. As discussed earlier, an electron can move into these holes and, in effect, the hole moves in the opposite direction. The abundance of holes creates P-type material, named for its positive charge due the lack of electrons or excess of holes. By joining this N-type and P-type material, diodes and transistors can be formed. DIODES Diodes block current flow in one direction and pass current in the opposite direction. This is accomplished by joining a layer of P type material and a layer of N- type material during manufacturing. Where they meet is called the PN junction. At the PN junction, some of the electrons of the N-type material move into some of the holes in the P-type material and create a neutral area at the junction. Another way of thinking of this is that the positive holes attract the negative electrons leaving no free electrons, so current is unable to flow past that point. This neutral area acts as a barrier, which is called the depletion region. SEMICONDUCTORS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 168. The depletion region is very thin and responds rapidly to voltage changes. It is here that current is either allowed to pass or is blocked. When the diode is connected in a circuit where the N-type material is connected to the negative terminal of the battery and the P-type material is connected to the positive terminal, the excess electrons in the N-type material are repelled by the negative potential of the battery. At the same time, the positively charged holes in the P-type material are repelled by the positive potential of the battery, resulting in a concentration of holes and electrons at the depletion region. When voltage applied to the diode is great enough (.5 to .7 volts) electrons in the N type material will move across the depletion region at the junction, filling holes in the P-type material and leaving holes in the N-type material. Electrons move through the diode to the positive terminal of the battery and holes move through the diode to the negative terminal of the battery. When this happens the diode conducts current and is said to be forward biased. If the connection of the diode in the circuit is reversed, with the N-type material connected to the positive terminal of the battery and the P-type material connected to the negative terminal, the diode is reverse biased. In this case, the electrons in the N-type material are attracted to the positive terminal of the battery and the holes in the P-type material are attracted to the negative terminal of the battery. This results in an increase in the depletion region or neutral zone so no current can flow through the diode. Whether the diode conducts or blocks current flow is determined by the voltage polarity applied to it. SEMICONDUCTORS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 169. If the reverse bias voltage applied to a diode is great enough, the voltage can overcome the depletion region at the junction and the diode will conduct for a short period before burning open. When this happens the diode is destroyed. The three main uses for diodes in the automobile are rectification, de-spiking, and isolation. Rectification—Since a diode will allow current to flow in one direction and not the other, it can be used to turn alternating current into direct current. This is called rectification. Diodes can provide either full-wave or half-wave rectification, depending on the number of diodes and how they are connected. A half-wave rectifier consisting of one diode will have an output voltage that is approximately one half of the AC source. Since the output from an AC power source continually changes or alternates from positive to negative, the diode is forward biased for part of the output and reverse biased for the other. The diode will allow current to flow in the circuit when it is forward biased but will block the flow of current when it is reverse biased. The result is that only half of the wave is output while the other half is blocked by the diode. This type of rectifier is not commonly found in an automotive application since it is not an efficient way to rectify AC to DC to charge a battery. A full-wave rectifier uses a four-diode network to rectify both halves of an AC output. In such a system, current flows from the first half of the phase of the AC power source through the first diode in forward bias, through the external circuit, through the second diode, then completes the circuit. On the second half of the phase, the current flows through the third diode, through the external circuit, through the fourth diode and completes the circuit. SEMICONDUCTORS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 170. By using four diodes in the full-wave rectifier, all of the current flows to the DC part of the circuit and the current in the DC part always flows the same direction even though the current flow in the AC power source changes directions. The full-wave, three-phase rectifier found in an automotive alternator goes a step further. Because the alternator uses three coils that produce three overlapping AC sine waves staggered at 120 degree intervals, six diodes are required to achieve full-wave rectification. Each coil uses four of the diodes to rectify the output, achieving full-wave rectification (as in the full-wave, single-phase rectifier discussed earlier). Because the coils and diodes are interconnected, the same diodes are used by different coils at different times. Due to the overlap of the waves, output from each coil in this type of alternator produces a smooth output to the DC system. The following worksheet shows how the six diodes can rectify the output of all three coils. SEMICONDUCTORS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 171. DIODE RECTIFICATION WORKSHEET In each of the illustrations above, trace the path of current flow through the stator coils, the corresponding diodes and the DC circuit. The arrows in the illustrations next to the stator coils show the direction of conventional current flow. SEMICONDUCTORS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 172. De-spiking—Diodes are used on some relay coils to suppress voltage spikes. These spikes can damage components such as transistors in the control circuit of the relay. The voltage spike is produced by the collapsing magnetic field in the relay coil which occurs whenever current flow through the coil is stopped suddenly. The voltage induced in the relay coil is similar to the way an ignition coil operates. The induced voltage in a relay coil can be several times more than the system voltage. A de-spiking diode is connected in parallel with the relay coil. It is reverse biased when the relay is turned on, therefore no current will flow through the diode. When the relay control circuit is opened, current stops flowing through the coil, causing the magnetic field to collapse. The magnetic lines of force cut through the coil and induce a voltage. Since the circuit is open, no current flows. The voltage builds until it reaches about .7 volts, enough to forward bias the diode, completing the circuit to the other end of the coil. The current flows around in the diode and coil circuit until the voltage is dissipated. Because some relays are located in very hot environments where de-spiking diodes can fail prematurely, resistors are sometimes used instead. The resistor is more durable and can suppress voltage spikes in much the same way as the diode, but the resistor will allow current to flow through it whenever the relay is on. Therefore resistance of the resistor must be fairly high (400 to 600 ohms) to prevent too much current flow in the circuit. Because of resistors' high resistance, they are not quite as efficient at suppressing a voltage spike as diodes. SEMICONDUCTORS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 173. Isolation—A diode can be used to separate two circuits. Diodes are used in this way on many Toyota models. The Electronic Load Sense (ELS) circuit used on a Camry is a good example. This system signals the ECU to increase the idle speed when certain electrical loads are turned on. It uses two diodes so two different circuits can provide a voltage signal to the same terminal on the ECU. Without diodes, whenever either of the systems were turned on, voltage would also be applied to the other circuit causing it to operate. SEMICONDUCTORS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 174. Zener diode—A zener diode acts like an ordinary silicon diode when in the forward bias direction, but it has been specially doped to act very differently in reverse bias. A zener diode allows current to flow in reverse bias at a specific voltage without damage over and over again. The reverse bias voltage at which the zener will conduct, sometimes called the zener point, differs from one zener to another as each zener diode is doped to have a zener point at a specific voltage. A zener diode can be used to suppress spikes by connecting it between the circuit and ground with the diode reverse biased. When a voltage spike exceeds the zener point of the diode, it completes the circuit to ground and prevents the spike from damaging anything. A more common use of a zener diode in an automobile is to sense the charging system voltage. By connecting the zener between the base of a transistor and the positive side of the charging system, the zener can allow current to flow to the base of the transistor when its zener point is reached. If the zener point is 14.5 volts and the transistor to which the zener is connected turns off alternator field current when the transistor is turned on, a constant charging system voltage can be maintained. As soon as the system voltage drops below the zener point, the diode stops conducting and the transistor turns off, allowing field current to flow. SEMICONDUCTORS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 175. Light emitting diodes (LEDs)—An LED is a diode that is specially designed to produce light. LEDs are made with a transparent epoxy case so they can emit the light they produce when forward biased. The color of the light given off by an LED can be red, green or infrared, depending on how the material is doped An LED, like a standard silicon diode, will conduct current in only one direction. The forward bias voltage drop of an LED (1.5 to 2 volts) is much higher than a silicon diode. The forward bias current through an LED must be controlled, as with any other semiconductor' or damage will result. LEDs have advantages over ordinary bulbs, such as longer life, cooler operation, lower voltage requirements and the ability to produce the same amount of light as an incandescent bulb while consuming less power. In vehicles, LEDs are used in a variety of ways, including displays and indicators. LEDs are also used in conjunction with phototransistors, which convert light to electrical current. A vehicle speed sensor, known as a photo-coupler or light-activated switch, is a good example. In a speed sensor, the speedometer cable is connected to a slotted wheel which separates the LED from the phototransistor. As the wheel turns, it constantly breaks the beam of light emitted from the LED to the phototransistor, thereby turning the phototransistor on and off. The pulsed signal goes to the computer and is used to determine vehicle speed. Taken with permission from the Toyota, Advanced Electrical Course#672 SEMICONDUCTORS Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 176. SEMICONDUCTORS ASSIGNMENT NAME: 1. Describe the construction and operation of a capacitor. 2. Name the three types of capacitors. 3. Describe the three uses of capacitors. 4. Name and explain both current flow theories. 5. Describe how a semicondor differs from a conductor or an insulator. 6. What are two common types of semiconductor material. 7. Explain what “Doping “ is and how N-Type or P-Type material is made. 8. Describe the function and construction of a “Diode”. 9. Explain the term PN junction. 10. Describe the depletion region of a diode. 11. What is the voltage drop (the voltmeter reading) of a diode? 12. Explain the terms “Forward” and “Reverse” Bias. 13. Describe Rectification and how diodes are used. 14. Explain the difference between half-wave and full-wave rectification. 15. Describe the function of a De-spiking (Voltage Suppression) diode. 16. Explain the operation of a De-spiking (Voltage Suppression) diode. 17. Describe the function of an Isolation diode. 18. Explain the operation of an Isolation diode. 19. Explain how a “Zener Diode” differs from a conventional diode. 20. Explain the term “Zener Point” (Avalanche Point) and what happens at this point. 21. Explain how a “Light Emitting Diode” (LED) differs from a conventional diode. 22. What is the voltage drop (the voltmeter reading) of an LED?
  • 177. THE BIPOLAR TRANSISTOR TRANSISTORS A transistor can be used as an amplifier to control electric motor speed such as AC blower motors, or as solid state switches to control actuators such as fuel injectors. This chapter will cover each of the following four areas: Transistor Operation Transistor Applications Transistor Gain Integrated Circuits Transistors are made from the same N- type and P-type materials as diodes and employ the same principles. Transistors, however, have two PN junctions instead of just one like a diode has. The two PN junctions allow a transistor to perform more functions than a diode, such as acting as a switch or an amplifier. The bipolar transistor is made up of three parts: the emitter, the base and the collector. There are two types of bipolar transistors: the PNP and the NPN. In the PNP transistor the emitter is made from P-type material, the base is N-type material and the collector is P-type material. For the PN transistor to operate, the emitter must be connected to positive, the base to negative and the collector to negative. The NPN transistor has an emitter made from N-type material. Its base is P-type material and the collector is N-type material. For the NPN transistor to operate, the emitter must be connected to negative, the base to positive and the collector to positive Aside from the way in which the NPN and PNP transistors are connected in the circa they operate the same way. Both transistor have a forward biased junction and a reverse biased junction, and three parts-the emitter, the base and the collector-formed in a three- layer arrangement TRANSISTORS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 178. Current flow between the emitter and base controls the current flow between the emitter and collector. The emitter of the transistor is the most heavily doped so it has the most excess electrons or holes, depending on whether the emitter is P- type or N-type material. The collector is doped slightly less than the emitter and the base is very thin with the fewest doping atoms. As a result of this type of doping, the current flow in the emitter- collector is much greater than in the emitter-base. By regulating the current at the emitter-base junction, the amount of current allowed to pass from the emitter to the collector can be controlled. The symbols for both PNP and NPN transistors are very similar. The distinguishing feature is the arrow, which is always located in the emitter and always points in the direction of conventional current flow. The base is part of the symbol which looks like a "T" and the remaining line, opposite the emitter, is the collector. In the symbol for a PNP transistor the arrow in the emitter points toward the center so the current flow is from emitter to base and from emitter to collector. In the NPN transistor the arrow in the emitter points away from the center so the current flow is from the base to emitter and from the collector to emitter. One of the most common uses of a transistor in an automobile is as a switch. Switching transistors can be found in solid state control modules and computers. They control devices on the car such as the fuel injector in an EFI car or a mechanical relay that operates the retract motor on a car with retractable headlights. When an NPN transistor is used as a switch, the emitter of the transistor is grounded and the base is connected to positive. If the voltage is removed from the base, no current flows from the emitter to the collector and the transistor is off. When the base is forward biased by a large enough voltage, current will flow from the emitter to the collector. Essentially, the transistor is being used to control a large current with a small current like a starter relay. A small amount of current to the relay will complete a circuit so a large current can flow. TRANSISTORS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 179. TRANSISTOR GAIN We know that the current flow between the emitter and base controls the current flow between the emitter and collector. Also, the amount of current flow between the emitter and base will affect the amount of emitter collector current. The ratio between these two currents is known as the "gain" of the transistor. This gain allows us to use a transistor to control a large current with a very small current similar to the way a relay operates. Example shown: if a transistor had a gain of 100 and the emitter-base current was increased by 10 milliamps or .01 amps, the emitter collector current would increase by 100 times or 1 amp. This type of increase will occur until the transistor reached saturation. This is the point where increasing the emitter-base current does not increase the emitter- collector current. Transistors used for switching usually operate at the saturation point when turned on, while transistors that are used for amplifiers operate in the range between off and saturation. Another application for a transistor is amplification. This situation takes advantage of the relationship between the emitter base current and the emitter- collector current. Since a small change in current flowing through the transistor from the emitter to the base has a proportionally larger effect on the emitter-collector current, we can use transistors to increase the strength of a small signal in a radio or to provide a variable control for a motor. On some Toyota models, transistors are being used to provide variable speed control such as the AC blower motor on the Cressida and the electric motor that runs the power steering pump on the 1991 MR2. By varying the emitter-base current of the transistor, the current flowing through the motor can be varied, thereby varying the motor speed. TRANSISTORS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 180. INTEGRATED CIRCUITS An integrated circuit (IC) is nothing more than many transistors, diodes, capacitors and resistors connected together with conductors and placed on a single silicon chip. A single IC is a system within a system, with several to several thousand electrical circuits built into or onto a several-squaremillimeter silicon chip in a ceramic or plastic package. The advantages of the IC are the size and low cost of mass production along with low power consumption and reliability. An IC can be anything from simple logic gate to a microprocessor to almost a complete computer on a chip. ICs are more reliable than non- integrated circuits because all the elements can be built into and onto a single silicon chip, thereby reducing contact junctions. In addition, the number of components is reduced. ICs are classified by the number of parts included on one chip. The Small Scale Integration (SSI) IC has about 100 elements; the Medium Scale Integration (MSI) IC has 100 to 1,000 elements; the Large Scale Integration (LSI) IC has 10,000 to 100,000 elements; and the Very Large Scale Integration (VLSI) IC has more than 100,000 elements. Taken with permission from the Toyota Advanced Electrical Course#672 TRANSISTORS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 181. TRANSISTORS ASSIGNMENT NAME: 1. Describe the basic construction of a Bipolar Transistor. 2. Draw a PNP Transistor and label its parts. 3 Explain the two current paths of a bipolar transistor. 4. Explain the purpose of the arrow on the emitter and why is the direction of it important. 5. If the arrow on the emitter is pointing toward the base. What type of transistor is it and what voltage signal (positive or negative) is needed to the base in order to forward bias the transistor? 6. Explain and provide an example of “transistor gain”. 7. Describe what an integrated circuit is.
  • 182. COMPUTERS AND LOGIC CIRCUITS Dealing with computers can seem overwhelming for those who are accustomed to working with mechanical systems. Since we cannot actually see what is going on inside the computer or the system it controls, computers may not be as easy to understand as mechanical components such as transmissions and engines. However, computers are not as complicated as they might sound. This chapter will help demystify computers. The computers found on a vehicle are really no different than any other computer encountered in everyday life. Vehicle computers rely on data from some type of input device and then follow the instructions in their programs to determine the required output. The input device may be a keyboard or a coolant temperature sensor, and the output may be video display or a fuel injector. The program the computer follows may be for word processing or for controlling fuel metering and engine timing. Computers can process a great deal of data very quickly and accurately, making them very useful for several jobs including controlling many of the systems on an automobile. This chapter explains how a computer functions, starting with the inputs and outputs, the computer's central processing unit (CPU) and memory, and logic gates and their symbols. Understanding how computers work is essential because most vehicles have some type of computer. Knowing how computers operate and fit together with various sensors and actuators will increase your ability to diagnose and repair problems. COMPUTERS AND LOGIC CIRCUITS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 183. This chapter is divided into the following sections: Analog and Digital Inputs Analog and Digital Outputs Signals, including. Analog and digital wave forms AID converters D/A converters Microprocessor Random Access Memory (RAM) Read-Only Memory (ROM) Programmable Read-Only Memory (PROM) Logic Circuits INPUTS As demonstrated in the previous chapter, the ECU, as well as any other automobile computer, depends on sensors to monitor various system functions and report their status back to the computer. Once the computer receives the data from the sensors, it analyzes it against pre- programmed standards and acts accordingly. One problem with many of these inputs is that they do not speak the same language as the computer. The computer only understands digital signals or on/off signals. A resistive type sensor provides the computer with a variable voltage, known as an analog signal. Some sensors, like the switch type sensors, do provide a digital signal for the computer. In this case, the computer can interpret the signal because it is either on or it is off-nothing in-between. Because computers must have digital inputs to use the data received, all analog signals must be converted to digital. How computers interpret the analog signals with an A/D converter will be covered later. OUTPUTS Computer output to most actuators is digital. The signal tells the actuator to either turn on for a specified length of time or shut off. Stepper motors, relays and solenoids have only two modes of operation: on or off. Again, when actuators require a variable voltage, such as the speed control for a blower motor for air conditioning, the computer needs another interpreter. In this case, the interpreter is a D/A converter, which will be covered later. SIGNALS As explained previously, the two types of signals are analog and digital. The voltage of these signals may change slowly or very quickly depending on the sensor and what it monitors. When signals are expressed as wave forms on an oscilloscope, the analog signal shows up as a flowing line with curved peaks and valleys, indicating variable rises and drops in voltage. The digital signal has vertical rises and drops, and a horizontal line with sharp corners. The top horizontal lines indicate when the voltage is high or on and the bottom horizontal lines indicate when the voltage is low or off. COMPUTERS AND LOGIC CIRCUITS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 184. When using a voltmeter to measure digital or analog signals that change very quickly, such as speed sensor or RPM signals, it is important to remember that the meter reading is not a true representation of the signal. A voltmeter displays the average reading of the signal. For example, with a digital signal the voltmeter will display the average between zero volts (off) and the voltage when the circuit was on. The computer looks for "on" signals, not voltage. The voltmeter, however, is looking for voltage, not whether a signal comes through. A voltmeter may show that the voltage is within specifications even if a pulse is missing. That missing signal could represent the cause of an engine problem. You might not know it by the voltmeter, causing you to assume incorrectly the problem is elsewhere and waste time searching. So if you suspect the problem is in a certain circuit, but the voltmeter does not show it, consider using an oscilloscope for a more accurate reading. At the very least, you should be aware of this voltmeter limitation with digital signals. When dealing with computer signals it is also important to remember that there is a difference between the signal source and the source of the voltage on the signal wire. This is especially important when a sensor input goes to more than one computer, such as a speed sensor signal, or if the signal is from one computer to another. One computer may supply the voltage to the sensor which toggles the voltage to ground, and the other computer may just monitor the signal. If a wire is disconnected from the computer that supplies voltage to the sensor, the signal is lost to both computers. Do not mistake this for a defective computer. Analog signals also have limitations in that their inputs are not usable by the computer until translated into digital signals. The A/D converter handles that translation. This takes us briefly back to computer language. Digital on/off can be represented by the binary numbering system of 0 (off) and 1 (on). Any decimal number (1, 2, 3, etc.) can be represented using O's and 1's so the computer understands. The several thousand transistors inside the computer's microprocessor can switch on and off in combinations that equal any binary number in a microsecond. COMPUTERS AND LOGIC CIRCUITS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 185. The A/D converter changes the analog signal to this binary language by taking samples of the analog signal at a frequency known as the sampling rate. The converter measures the wave and assigns a digital value to it. The higher the sampling rate, the closer the digital signal comes to representing the analog one. In most cases each sample is divided into eight bits. Each bit is assigned either a "0" or a "1". These eight bits are called a word. As illustrated (below), whenever the A/D converter samples the signal, it assigns a binary number to the voltage at that point (which the computer reads as a series of "ONs" and "OFFs"), and slices up the wave like a loaf of bread. With the signal converted to eight-bit words, the computer can use the data from the sensor. The computer then sends out instructions in the form of a digital signal to an actuator. In most cases this works because most actuators are solenoids or stepper motors which operate on digital commands. There are, however, some components such as blower motors or the power steering pump motor on the 1991 MR2, that require variable voltage to operate motors at variable speeds. In such cases, the computer uses a D/A converter to change the digital signal to analog. The principles of D/A converter operation are the same as the A/D converter. The pulses of voltage coming from the computer are converted to variable voltage. THE MICROPROCESSOR The microprocessor is the heart of the computer. It is also called the central processing unit (CPU). Again, keep in mind that the CPU does not perform complicated operations. Instead, it performs thousands of simple operations incredibly fast. To keep all of the operations the CPU performs from becoming entangled, it executes them in order, paced by a clock. The CPU can be divided into three sections: the control section, the arithmetic and logic section, and the register section. The control section controls the computer's basic operations. It is programmed with instructions from a memory to handle these chief operations: Sending data from one part of the computer to another Data input and output to and from the computer Arithmetic calculations Halting computer operations Jumping to another instruction during the running of a program The arithmetic and logic section carries out the actual processing of data, which consists of arithmetic operations and logical operations. COMPUTERS AND LOGIC CIRCUITS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 186. The register section temporarily stores data or programs until they are sent to the arithmetic and logic section or the control section COMPUTER MEMORY Computers have their own filing system, known as "memory," which is the internal circuitry where programs and data are stored. Computer memory is divided into separate addresses to which data is sent y the CPU. The CPU then knows where to find that data when it is needed. Computers use their main memories for large amounts of data or program information. There are two kinds of memory: random access memory (RAM) and read-only memory (ROM). RANDOM ACCESS MEMORY (RAM) RAM is memory which the computer can both read from and write to. This is where the computer stores data received front sensors, such as engine RPM or coolant temperature. RAM works like thousands of toggle switches which can be either on or off to represent 0's and 1's. This is how the data is stored in RAM. The switches work like spring loaded switches, therefore they must be held in the on" position electrically. If power is lost, everything stored in RAM is lost. In most of the computers used on Toyotas, the RAM is divided into two sections. One section receives its power from the ignition switch. This is where data about operating conditions, such as vehicle speed and coolant temperature, is stored. The other section, called Keep Alive Memory, is powered directly by the battery. Information such as diagnostic codes is stored in Keep Alive Memory so that it is retained after the ignition is off. This is why a fuse or battery cable has to be removed to clear diagnostic codes. COMPUTERS AND LOGIC CIRCUITS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 187. READ-ONLY MEMORY (ROM) This is where the basic operating instructions for the computer are located. The instructions are built into the chip when it is manufactured and cannot be changed. The computer can only read the information located in ROM and cannot write to it or use it to store data. Since the information in ROM is built in during manufacture, it is not lost when power is removed. PROGRAMMABLE READ-ONLY MEMORY (PROM) A PROM is like a ROM except it can be programmed or have information written to it once. This is done before it is installed in the computer. The computer can only read from the PROM and cannot write to it. The PROM contains the specific program instructions for the computer, such as the timing advance curve for a particular engine or the shift points for an automatic transmission. There are other types of programmable ROM being used, such as erasable programmable read only memory (EPROM) which can be erased by ultraviolet light and reprogrammed. Another type is electronically erasable programmable read only memory (EEPROM) which can be erased electronically and reprogrammed. This is all done outside of the computer by the manufacturer. NON-VOLATILE MEMORY Some computers use a type of RAM that is non-volatile, meaning that it retains its memory when the power is removed. This type of memory can only be erased by going through a specific procedure. This is the type of memory used to store code 41 in the SRS air bag system on Celica and Supra. LOGIC CIRCUITS As computers and solid state control modules become more prevalent on automobiles, some of the logic gate symbols that represent their internal circuits will show up more often. It is necessary to know not only what the logic symbols stand for, but to understand the basic operation of the circuits they represent when you analyze wiring diagrams during troubleshooting. Therefore, you should know a little about logic circuits and the symbols used to represent them. A logic gate symbol is simply a shorthand way of representing an electronic circuit that operates in a certain way. Understanding the logic symbols can make understanding the operation of a circuit much quicker and easier than if the circuit were represented by showing all the transistors, diodes and resistors. The logic symbols shown in diagrams in the EWD and New Car Feature book show what pin voltages must be present for an electronic controller to function properly. Again, anything connected with a computer is based on the digital on/off language. The same holds true for logic circuits, which are made up of transistors combined in units called "gates." These gates process two or more signals logically. In essence, they are switches. Depending on the input voltage, the gate or switch will be either on or off. The first thing to learn about the different gates is their symbols. Once you know the symbols and how each gate works, diagnosing a computer related problem will be easier. COMPUTERS AND LOGIC CIRCUITS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 188. COMPUTERS AND LOGIC CIRCUITS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 189. COMPUTERS AND LOGIC CIRCUITS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 190. COMPUTERS AND LOGIC CIRCUITS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 191. COMPUTERS AND LOGIC CIRCUITS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 192. Taken with permission from the Toyota Advanced Electrical Course#672 COMPUTERS AND LOGIC CIRCUITS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 193. COMPUTERS AND LOGIC CIRCUITS ASSIGNMENT NAME: 1. Explain both the purpose and different types of inputs used by the computer. 2. Name the type of output signal most often used by the computer. 3. Name the components that are typically used as output devices. 4. Explain the difference between Analog and Digital Signals. 5. Explain both the purpose and complete name of an A/D converter. 6. Draw both an Analog and Digital signal. 7. Explain the binary numbering system and why it is used. 8. Explain the function of the Microprocessor. 9. Describe the purpose of the RAM (Random Access Memory) 10. Describe the purpose of the ROM (Read Only Memory) 11. Describe the purpose of the PROM (Programmable Read Only Memory) 12. Explain the basic function and list the truth table of an “AND” logic gate circuit. 13. Draw the equivalent mechanical circuit of an “AND” logic gate circuit. 14. Explain the basic function and list the truth table of an “OR” logic gate circuit. 15. Draw the equivalent mechanical circuit of an “OR” logic gate circuit. 16. Describe the basic function and list the truth table of a “NOT” logic gate circuit. 17. Describe the basic function and list the truth table of a “NAND” logic gate circuit. 18. Describe the basic function and list the truth table of a “NOR” logic gate circuit. 19. Describe are the two basic components of a “FLIP-FLOP” logic gate circuit.
  • 194. SENSORS AND ACTUATORS Computer controlled systems continually monitor the operating condition of today's vehicles. Through sensors, computers receive vital information about a number of conditions, allowing minor adjustments to be made far more quickly and accurately than mechanical systems. Sensors convert temperature, pressure, speed, position and other data into either digital or analog electrical signals. A digital signal is a voltage signal that is either on or off with nothing in between. A switch is the simplest type of digital signal sensor. The signal from the switch could be 0 volts when off and 12 volts when on. Analog signals on the other hand have continuously variable voltage. A good example is the coolant temperature sensor. The coolant temperature sensor may vary the voltage signal anywhere between 0 volts and 5 volts depending on the temperature of the engine. SENSORS & ACTUATORS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 195. The digital signal is the easiest for the computer to understand because it reads the signal as either "on" or "off." The analog signal must be conditioned or converted to digital so the computer can understand it. (This will be covered later.) While a vehicle may have many different sensors, there are three main categories: voltage-generating, resistive and switches. A voltage-generating sensor generates its own voltage signal in relation to the mechanical condition it monitors. This signal in turn relays to the computer data about the condition of the system it controls. A resistive sensor reacts to changes in mechanical conditions through changes in its resistance. The computer supplies a regulated voltage or reference voltage to the sensor and measures the voltage drop across the sensor to determine the data. Switch sensors toggle a voltage from the computer high or low, or supply an "on" or "off" voltage signal to the computer. This type of sensor may be as simple as a switch on the brake pedal or as complex as a phototransistor speed sensor. The computer uses the sensor data to control different systems on a vehicle through the use of actuators. An actuator is an electromechanical device such as a relay, solenoid or motor. Actuators can adjust engine idle speed, change suspension height or regulate the fuel metered into the engine. This chapter describes several specific sensors used in automobiles, such as potentiometers, thermistors and phototransistor / LED combinations. This chapter also addresses actuators that complete the control process by carrying out the computer's instructions. The Sensors and Actuators section is divided into the following areas: Resistive sensors: potentiometers thermistors piezo resistive Voltage generating sensors: piezo electric zirconia-dioxide magnetic inductance Switch sensors: phototransistors and LEDs speed sensors G-sensors (Air Bag Impact Sensors) Actuators: stepper motors solenoids RESISTIVE SENSORS Potentiometers A potentiometer is a variable resistor that is commonly used as a sensor. A potentiometer has three terminals: one for power input, one for a ground and one to provide a variable voltage output. A potentiometer is a mechanical device whose resistance can be varied by the position of the movable contact on a fixed resistor. The movable contact slides across the resistor to vary the resistance and as a result varies the voltage output of the potentiometer. The output becomes higher or lower depending on whether the movable contact is near the resistor's supply end or ground end. SENSORS & ACTUATORS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 196. The vane type air flow meter on an EFI equipped vehicle is a common location on a Toyota for a sensor that uses a potentiometer. This sensor converts the air flow meter vane opening angle to a voltage and sends it to the Electronic Control Unit (ECU). This signal allows the ECU to determine the volume of air that is entering the engine. Some models also use a potentiometer as the throttle position sensor. The potentiometer in this case is attached to the throttle shaft of the throttle body. As the shaft is rotated the voltage output of the potentiometer changes. The voltage output of the potentiometer supplies data to the ECU about the throttle opening angle. Thermistors Thermistors are variable resistors whose resistance changes in relation to temperature. Thermistors can have either a negative temperature coefficient (NTC) or a positive temperature coefficient (PTC). A thermistor with a negative temperature coefficient will decrease in resistance as the temperature is increased. On the other hand, a thermistor with a positive temperature coefficient will increase in resistance as the temperature is increased. The thermistor has two terminals, one for power and one for ground. A reference voltage is supplied to one terminal through a fixed series resistor located inside the computer. The other terminal of the thermistor is connected to ground, usually back through the computer. The computer monitors the voltage after the internal fixed resistor and compares this voltage to the reference voltage to determine the temperature of the thermistor. The relationship between the two voltages changes as the temperature of the thermistor changes. SENSORS & ACTUATORS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 197. The coolant temperature sensor and the air temperature sensor in the air flow meter are both NTC thermistors. Thermistors are also used as sending units for temperature gauges such as the coolant temperature gauge. The TCCS ECU uses data from the coolant temperature sensor and air temperature sensor to help determine the proper amount of fuel and how long to open the fuel injectors. The ECU also uses this data to determine how much the ignition timing should be advanced as well as the proper setting for the ISC to maintain the proper idle speed. When either the air temperature or the coolant temperature is low, the respective thermistor's resistance increases and the computer receives a high voltage signal at the respective sensor wire. Conversely, a high temperature at either sensor results in a low voltage signal due to the lower resistance of the thermistor. Piezo Resistive A piezo resistive sensor is a resistor circuit constructed on a thin silicon wafer. Physically flexing or distorting the wafer a small amount changes its resistance. This type of sensor is usually used as a pressure sensing device such as a manifold pressure sensor, although it may also be used to measure force or flex in an object such as the deceleration sensor located in the SRS air bag center sensor. One of the most important piezo resistive sensors is the manifold pressure sensor which monitors the air intake volume for Electronic Fuel Injection (EFI). The signal it sends to the ECU determines the basic fuel injection duration and ignition advance angle. Within the sensor is a silicon chip combined with a vacuum chamber. One side of the chip is exposed to the intake manifold pressure and the other side to the internal perfect vacuum in the chamber. A change in the intake manifold pressure causes the shape of the silicon chip to change, with the resistance value of the chip fluctuating in relation to the degree of deformation. An integrated circuit converts the fluctuation to a voltage signal that is sent to the ECU, where the air-fuel ratio is regulated. The sensor has three external terminals: one for power, one for ground and one to provide the voltage signal to the computer. The voltage signal varies with the pressure in the intake manifold. Another use for this same type of sensor is to sense turbocharger boost. On turbocharged engines, the sensor is used to measure pressures that are higher than atmospheric pressure and to supply corresponding voltage signals to the ECU. To prevent engine damage, the ECU can cut off the fuel being injected if the manifold pressure becomes too high. SENSORS & ACTUATORS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 198. VOLTAGE GENERATING SENSORS Piezo Electric Piezo electricity is generated by pressure on certain crystals, such as quartz, which will develop a potential difference, or voltage, on the crystal face. When the crystal flexes or vibrates, an AC voltage is produced. Knock sensors, which are becoming more common, take advantage of this phenomenon by sending the ECU a signal that engine knock is occurring. The ECU in turn retards the ignition timing to stop the knocking. Knock sensors contain a piezo electric element which, when deformed by cylinder block vibration caused by knocking, generates a voltage. There are two styles of knock sensors used. The mass type produces a voltage output over wide range, but the signal is greatest at a vibration of approximately 7 kHz. The other style is the resonance type which only produces a significant voltage signal when exposed to a vibration of approximately 7 kHz. Since the voltage output from either knock sensor varies continually, the system is highly susceptible to electromagnetic and radio interference. The computer can be fooled by these stray electrical signals if they get mixed with the knock sensor signal. For this reason the signal wire running from the sensor to the ECU is a special ground- shielded type. The shield surrounds the signal wire and is connected to ground so any electrical interference is taken to ground. If this shield is damaged or not grounded, the electrical interference can reach the ECU and cause it to retard the timing unnecessarily. Oxygen Sensors The oxygen sensor, located in the exhaust manifold, senses whether the air-fuel ratio is rich or lean, and sends signals to the ECU which in turn makes minor corrections to the amount of fuel being metered. This is necessary for the three-way catalytic converter to function properly. There are two kinds of oxygen sensors: zirconia and titania. The zirconia oxygen sensor is constructed in a bulb configuration from zirconia dioxide. A thin platinum plate is attached to both the inside and outside of the bulb. The inner area is exposed to the atmosphere and the outside is exposed to the exhaust. When the sensor is heated to approximately 600˚F, electrically SENSORS & ACTUATORS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 199. charged oxygen ions form on the platinum plates. The amount of oxygen to which each plate is exposed determines how many ions form on the plates. When there is a difference in the number of ions on the plates, a difference in potential or voltage occurs between the two plates. The less oxygen there is in the exhaust, the greater the voltage produced. When the air-fuel mixture is lean, the voltage created is low. Conversely, when the mixture is rich, the voltage is high. The titania oxygen sensor does not produce a voltage. Instead, it undergoes a change in resistance in relation to the oxygen content in the exhaust. This type of oxygen sensor is referred to as a thick film sensor. It consists of a piece of titania with two wires connected to it located at the end of an insulator. The sensor is not exposed to the atmosphere only to the exhaust. Because the operating temperature must remain constant, the sensor has an electric heater. After the sensor is at operating temperature, the amount of oxygen to which the titania is exposed. will change the physical resistance of the sensor. The ECU supplies a reference voltage to the sensor and monitors the voltage at the signal wire, similar to a thermistor. Magnetic Inductance Magnetic inductance sensors consist of a coil of wire around an iron core plus a permanent magnet. The magnet can be either stationary or movable. If the magnet is the moving member, as it passes the coil the magnetic lines of force cut through the coil and a voltage is produced. Since the north and south poles of the magnet alternate as they pass the coil, the voltage polarity also alternates. As the speed of the magnet rotating past the coil is increased a larger voltage is produced and the frequency of the voltage polarity changes is increased. This same type of sensor can also work if the magnet is stationary and attached to the core of the coil. When a toothed reluctor, or rotor (made from a magnetic material) is rotated past the coil and magnet, the magnetic lines of force move and cut through the coil. The lines of force cutting through the coil will produce the same type of voltage output as when the magnet was moving. SENSORS & ACTUATORS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 200. This type of sensor is commonly used as a wheel speed sensor on ABS equipped vehicles. This sensor is also used in the distributor to determine RPM and crankshaft position. Since the voltage output of this sensor is varying continually and is low at low speeds, the computer must be able to sense the small voltage. If electrical interference is allowed to combine with the signal voltage, the computer could be fooled. To prevent stray electrical interference, the signal wire usually has a ground shield formed around it like the knock sensor. SWITCH TYPE SENSORS Phototransistor and LED As discussed in the previous chapter, a phototransistor is a transistor that is activated or turned on by light. When combined with a LED and a rotating slotted wheel in a vehicle speed sensor, a phototransistor can supply vehicle speed data to a computer. In this type of sensor the LED is aimed at the phototransistor. When the slotted wheel is rotated by the speedometer cable, it breaks the beam of light. The beam of light is interrupted 20 times per revolution. The ECU supplies a reference voltage to the collector of the phototransistor and the emitter is connected to ground. Each time the light hits the phototransistor, it turns it on just like a toggle switch. Each time the phototransistor is turned on, the wire from the ECU is connected to ground and the voltage is pulled down to 0 volts. The ECU can count these pulses and calculate vehicle speed. This type of sensor is also used as a G Sensor or deceleration sensor on the Celica All Trac and Trucks equipped with ABS. This sensor has two LEDs aimed at two phototransistors that are separated by a slotted plate on a fulcrum. When the vehicle is decelerated, the plate pivots on the fulcrum and the slots in the plate line up with one or the other or both of the LEDs and phototransistors-depending on the rate of deceleration. These signals are sent to the computer so it can determine the deceleration rate for ABS to operate properly. SENSORS & ACTUATORS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 201. Reed Switches The reed switch is commonly used as a speed sensor or position sensor. It consists of a set of contacts that open when adjacent to a magnet. In the speed sensor application, the magnet is attached to the speedometer cable and rotates with the cable. Each time one of the poles of the magnet passes the switch the contacts open and then close. A voltage is supplied to one contact on the switch and the other contact is connected to ground. Each time the points close, the voltage is pulled down to 0 volts, just like the phototransistor speed sensor. ACTUATORS Stepper Motor Essentially, stepper motors are digital actuators; in other words, they are either on or off. They move in fixed increments in both directions, and can have over 120 steps of motion. Stepper motors are commonly used to enable the ECU to control idle speed. In most fuel injection systems, the stepper motor controls an idle air bypass built into the throttle body. SENSORS & ACTUATORS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 202. In an idle speed control valve (ISCV), (located in the air intake chamber) a stepper motor is built into the ISCV where it rotates a valve shaft either in or out. This in turn increases or decreases the clearance between the valve and the valve seat, thereby regulating the amount of air allowed to pass through. The ISCV stepper motor allows 125 possible valve opening positions. Solenoids Like stepper motors, solenoids are digital actuators. One terminal is attached to battery voltage while the other is attached to the computer which opens and closes the ground circuit as needed. When energized, the solenoid may extend a plunger or armature to control functions such as vacuum flow to various emission-related systems or fuel injection. Most actuators are solenoids. Solenoids are controlled two ways: pulse width or duty cycle. Pulse width control is used when the frequency is not consistent. An example of pulse width is a fuel injector which is turned on for a determined length of time and then shut off. Duty cycle control is used when the frequency does remain constant. A duty cycle solenoid in ABS is designed to be on and off for a specific time according to a selected ratio-on for 20% of the time and off the other 80%. Idle speed control valves can be constructed with a solenoid instead of a stepper motor. In this case, the function is the same: the ECU sends a signal to the ISCV to control the intake air. Solenoid valves are also used in ECT transmissions. Shifting is controlled by the solenoid as it opens or closes a hydraulic passage to control oil flow to the shift valves. SENSORS & ACTUATORS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 203. SENSORS & ACTUATORS ASSIGNMENT NAME: 1. Describe the term “Digital Signal” and provide an example. 2. List three types of “Resistive senors” and provide an example of each. 3. List three “types of Voltage generating sensors” and provide an example of each. 4. List three types of “Switch sensors” and provide an example of each. 5. List two types of “Actuators” and provide an example of each. 6. Describe the operation of both types of “thermistors” and draw an example of the electrical circuit. 7. Explain the operation of a “Piezo Resistive” sensor. 8. Explain how a “Piezo Resistive” sensor differs from a “Piezo Electric” sensor. 9. Describe the operation and construction of the two basic types of Oxygen Sensors. 10. Outline the construction and common uses of a “Magnetic Inductance” sensor. 11. Outline the construction and common uses of a “Phototransistor” switch. 12. Explain the operation of a “Reed” switch and how they are used. 13. Describe the basic operation of a “stepper motor” and how they are used. 14. Explain two ways in which solenoids can be controlled.
  • 204. Electronic Control Transmission (ECT) The Electronic Control Transmission is an automatic transmission which uses modern electronic control technologies to control the transmission. The transmission itself, except for the valve body and speed sensor, is virtually the same as a full hydraulically controlled transmission, but it also consists of electronic parts, sensors, an electronic control unit and actuators. The electronic sensors monitor the speed of the vehicle, gear position selection and throttle opening, sending this information to the ECU. The ECU then controls the operation of the clutches and brakes based on this data and controls the timing of shift points and torque converter lock-up. Driving Pattern Select Switch The pattern select switch is controlled by the driver to select the desired driving mode, either "Normal" or "Power." Based on the position of the switch, the ECT ECU selects the shift pattern and lock-up accordingly. The upshift in the power mode will occur later, at a higher speed depending on the throttle opening. For example, an upshift to third gear at 50% throttle will occur at about 37 mph in normal mode and about 47 mph in power mode. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 205. The ECU has a "PWR" terminal but does not have a "Normal" terminal. When "Power" is selected, 12 volts are applied to the "PWR" terminal of the ECU and the power light illuminates. When "Normal" is selected, the voltage at "PWR" is 0 volts. When the ECU senses 0 volts at the terminal, it recognizes that "Normal" has been selected. Beginning with the 1990 MR2 and Celica and the 1991 Previa, the pattern select switch was discontinued. In the Celica and Previa systems, several shift patterns are stored in the ECU memory. Utilizing sensory inputs, the ECU selects the appropriate shift pattern and operates the shift solenoids accordingly. The MR2 and 1993 Corolla have only one shift pattern stored in the ECU memory. Neutral Start Switch The ECT ECU receives information on the gear range into which the transmission has been shifted from the shift position sensor, located in the neutral start switch, and determines the appropriate shift pattern. The neutral start switch is actuated by the manual valve shaft in response to gear selector movement. The ECT ECU only monitors positions "T' and "L." If either of these terminals provides a 12-volt signal to the ECU, it determines that the transmission is in neutral, second gear or first gear. If the ECU does not receive a 12-volt signal at terminals "T' or "1," the ECU determines that the transmission is in the "D" range. Some neutral start switches have contacts for all gear ranges. Each contact is attached to the gear position indicator lights if the vehicle is so equipped. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 206. In addition to sensing gear positions, the neutral switch prevents the starter from cranking the engine unless it is in the park or neutral position. In the park and neutral position, continuity is established between terminals "B" and "NB" of the neutral start switch illustrated below. Throttle Position Sensor This sensor is mounted on the throttle body and electronically senses how far the throttle is open and then sends this data to the ECU. The throttle position sensor takes the place of throttle pressure in a fully hydraulic control transmission. By relaying the throttle position, it gives the ECU an indication of engine load to control the shifting and lock-up timing of the transmission. There are two types of throttle sensors associated with ECT transmissions. The type is related to how they connect to the ECT ECU. The first is the indirect type because it is connected directly to the engine ECU, and the engine ECU then relays throttle position information to the ECT ECU. The second type is the direct type which is connected directly to the ECT ECU. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 207. Indirect Type This throttle position sensor converts the throttle valve opening angle into voltage signals. It has four terminals: VC, VTA, IDL and E. A constant 5 volts is applied to terminal VC from the engine ECU. As the contact point slides along the resistor with throttle opening, voltage is applied to the VTA terminal. This voltage increases linearly from 0 volts at closed throttle to 5 volts at wide- open throttle. The engine ECU converts the VTA voltage into one of eight different throttle opening angle signals to inform the ECT ECU of the throttle opening. These signals consist of various combinations of high and low voltages at ECT ECU terminals as shown in the chart below. The shaded areas of the chart represent low voltage (about 0 volts). The white areas represent high voltage (L1, L2, U: about 5 volts; IDL: about 12 volts). TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 208. When the throttle valve is completely closed, the contact points for the IDL signal connect the IDL and E terminals, sending an IDL signal to the ECT ECU to inform it that the throttle is fully closed. As the ECT ECU receives the L1, L2 and D signals, it provides an output voltage from 1 to 8 volts at the TT or ECT terminal of the diagnostic check connector. The voltage signal varies depending on the throttle opening angle and informs the technician whether or not the throttle opening signal is being input properly. Direct Type With this type of throttle sensor, signals are input directly to the ECT ECU from the throttle position sensor. Three movable contact points rotate with the throttle valve, causing contacts L1, L2, L3 and IDL to make and break the circuit with contact E (ground). The grid which the contact points slide across is laid out in such a way as to provide signals to the ECT ECU depicted in the chart below. The voltage signals provided to the ECT ECU indicate throttle position just as they did in the indirect type of sensor. If the idle contact or its circuit on either throttle sensor malfunctions, certain symptoms occur. If it is shorted to ground, lock-up of the torque converter will not occur. If the circuit is open, neutral to drive squat control does not occur and a harsh engagement may be the result. If the L1, L2, L3 signals are abnormal, shift timing will be incorrect. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 209. Water Temperature Sensor The water temperature sensor monitors engine coolant temperature and is typically located near the cylinder head water outlet. A thermistor is mounted within the temperature sensor, and its resistance value decreases as the temperature increases. Therefore, when the engine temperature is low, resistance will be high. When the engine coolant is below a predetermined temperature, the engine performance and the vehicle's drivability would suffer if the transmission were shifted into overdrive or the converter clutch were locked-up. The engine ECU monitors coolant temperature and sends a signal to terminal OD1 of the ECT ECU. The ECU prevents the transmission from upshifting into overdrive and lock-up until the coolant has reached a predetermined temperature. This temperature will vary from 122'F to 162’F depending on the transmission and vehicle model. For specific temperatures, refer to the ECT Diagnostic Information chart in the appendix of this book. Some models, depending on the model year, cancel upshifts to third gear at lower temperatures. This information is found in the appendix and is indicated in the heading of the OD Cancel Temp column of the ECT Diagnostic Information chart by listing in parenthesis the temperature for restricting third gear. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 210. Speed Sensors To ensure that the ECT ECU is kept informed of the correct vehicle speed at all times, vehicle speed signals are input into it by two speed sensors. For further accuracy, the ECT ECU constantly compares these two signals to see whether they are the same. The speed sensor is used in place of governor pressure in the conventional hydraulically controlled transmission. Main Speed Sensor (No. 2 Speed Sensor) The main speed sensor is located in the transmission housing. A rotor with built-in magnet is mounted on the drive pinion shaft or output shaft. Every time the shaft makes one complete revolution, the magnet activates the reed switch, causing it to generate a signal. This signal is sent to the ECU, which uses it in controlling the shift point and the operation of the lock-up clutch. This sensor outputs one pulse for every one revolution of the output shaft. Beginning with the 1993 Corolla A245E, the No. 2 speed sensor has been discontinued and only the No. 1 speed sensor is monitored for shift timing. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 211. Back- Up Speed Sensor (No.1 Speed Sensor) The back-up speed sensor is built into the combination meter assembly and is operated by the speedometer cable. The sensor consists of an electrical reed switch and a multiple pole permanent magnet assembly. As the speedometer cable turns, the permanent magnet rotates past the reed switch. The magnetic flux lines between the poles of the magnet cause the contacts to open and close as they pass. The sensor outputs four pulses for every one revolution of the speedometer cable. The sensor can also be a photocoupler type which uses a photo transistor and light-emitting diode (LED). The LED is aimed at the phototransistor and separated by a slotted wheel. The slotted wheel is driven by the speedometer cable. As the slotted wheel rotates between the LED and photo diode, it generates 20 light pulses for each rotation. This signal is converted within the phototransistor to four pulses sent to the ECU. Speed Sensor Failsafe If both vehicle speed signals are correct, the signal from the main speed sensor is used in shift timing control after comparison with the output of the back-up speed sensor. If the signals from the main speed sensor fail, the ECU immediately discontinues use of this signal and uses the signals from the back-up speed sensor for shift timing. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 212. Stop Light Switch The stop light switch is mounted on the brake pedal bracket. When the brake pedal is depressed, it sends a signal to the STP terminal of the ECT ECU, informing it that the brakes have been applied. The ECU cancels torque converter lock-up when the brake pedal is depressed, and it cancels "N" to "D" squat control when the brake pedal is not depressed and the gear selector is shifted from neutral to drive. Overdrive Main Switch The overdrive main switch is located on the gear selector. It allows the driver to manually control overdrive. When it is turned on, the ECT can shift into overdrive. When it is turned off, the ECT is prevented from shifting into overdrive. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 213. O/D Main Switch ON When the O/D switch is in the ON position, the electrical contacts are actually open and current from the battery flows to the OD2 terminal of the ECT ECU as shown below. O/D Main Switch OFF When the O/D switch is in the OFF position, the electrical contacts are actually closed and current from the battery flows to ground and 0 volts is present at the OD2 terminal as shown below. At the same time, the O/D OFF indicator is illuminated. Solenoid Valves Solenoid valves are electro-mechanical devices which control hydraulic circuits by opening a drain for pressurized hydraulic fluid. Of the solenoid valves, No. 1 and No. 2 control gear shifting while No. 3 controls torque converter lock-up. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 214. No. 1 and No. 2 Solenoid Valves These solenoid valves are mounted on the valve body and are turned on and off by electrical signals from the ECU, causing various hydraulic circuits to be switched as necessary. By controlling the two solenoids' on and off sequences, we are able to provide four forward gears as well as prevent upshifts into third or fourth gear. The No. 1 and No. 2 solenoids are normally closed. The plunger is spring loaded to the closed position, and when energized, the plunger is pulled up, allowing line pressure fluid to drain. The operation of these solenoids by the ECT ECU is described on pages 16- 19. No. 3 Solenoid Valve This solenoid valve is mounted on the transmission exterior or valve body. It controls line pressure which affects the operation of the torque converter lock-up system. This solenoid is either a normally open or normally closed solenoid. The A340E, A340H, A540E and A540H transmissions use the normally open solenoid. No. 4 Solenoid Valve This solenoid is found exclusively on the A340H transfer unit described on page 152 of this book. This solenoid is a normally closed solenoid which controls the shift to low 4-wheel drive. It is controlled by the ECT ECU when low 4-wheel drive has been selected at vehicle speeds below 18 mph with light throttle opening. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 215. Functions of ECT ECU Control of Shift Timing The components which make up this system include: • OD main switch • OD Off indicator light • ECT ECU • Water temperature sensor • Cruise control ECU • No. 1 and No. 2 solenoid valves (shift solenoids) The ECU controls No. 1 and No. 2 solenoid valves based on vehicle speed, throttle opening angle and mode select switch position. The ECT ECU prevents an upshift to overdrive under the following conditions: • Water temperature is below 122'F to 146*F*. • Cruise control speed is 6 mph below set speed. • OD main switch is off (contacts closed). In addition to preventing the OD from engaging below a specific engine temperature, upshift to third gear is also prevented in the Supra and Cressida below 96'F and the V6 Camry below 100’F. * Consult the specific repair manual or the ECT Diagnostic Information Technician Reference Card for the specific temperature at which overdrive is enabled. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 216. Control of Lock-Up The ECT ECU has lock-up clutch operation pattern for each driving mode (Normal and Power) programmed in its memory. The ECU turns the No. 3 solenoid valve on or off according to vehicle speed and throttle opening signals. The lock-up control valve changes the fluid passages for the converter pressure acting on the torque converter piston to engage or disengage the lock-up clutch. In order to turn on solenoid valve No. 3 to operate the lock-up system, the following three conditions must exist simultaneously: • The vehicle is traveling in second, third, or overdrive ("D" range). • Vehicle speed is at or above the specified speed and the throttle opening is at or above the specified value. • The ECU has received no mandatory lock-up system cancellation signal. The ECU controls lock-up timing in order to reduce shift shock. If the transmission up-shifts or down-shifts while the lock-up is in operation, the ECU deactivates the lock-up clutch. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 217. The ECU will cancel lock-up if any of the following conditions occur: • The stop light switch comes on. • The coolant temperature is below 122'F to 145’F depending on the model. Consult the vehicle repair manual or the ECT Diagnostic Information Technician Reference Card. • The IDL contact points of the throttle position sensor close. • The vehicle speed drops about 6 mph or more below the set speed while the cruise control system is operating. The stop light switch and IDL contacts are monitored in order to prevent the engine from stalling in the event that the rear wheels lock up during braking. Coolant temperature is monitored to enhance drivability and transmission warm-up. The cruise control monitoring allows the engine to run at higher rpm and gain torque multiplication through the torque converter. Neutral to Drive Squat Control When the transmission is shifted from the neutral to the drive range, the ECU prevents it from shifting directly into first gear by causing it to shift into second or third gear before it shifts to first gear. It does this in order to reduce shift shock and squatting of the vehicle. Engine Torque Control To prevent shifting shock on some models, the ignition timing is retarded temporarily during gear shifting in order to reduce the engine's torque. The TCCS and ECT ECU monitors engine speed signals (Ne) and transmission output shaft speed (No. 2 speed sensor) then determines how much to retard the ignition timing based on shift pattern selection and throttle opening angle. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 218. Fail-Safe Operation The ECT ECU has several fail-safe functions to allow the vehicle to continue operating even if a malfunction occurs in the electrical system during driving. The speed sensor fail-safe has already been discussed on page 8. Solenoid Valve Back-Up Function In the event that the shift solenoids malfunction, the ECU can still control the transmission by operating the remaining solenoid to put the transmission in a gear that will allow the vehicle to continue to run. The chart below identifies the gear position the ECU places the transmission if a given solenoid should fail. Notice that if the ECU was not equipped with fail-safe, the items in parenthesis would be the normal operation. But because the ECU senses the failure, it modifies the shift pattern so the driver can still drive the vehicle. For example, if No. 1 solenoid failed, the transmission would normally go to overdrive in drive range first gear. But instead, No. 2 solenoid turned it on to give 3rd gear. Should both solenoids malfunction, the driver can still safely drive the vehicle by operating the shift lever manually. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 219. ECT Shift Valve Operation Two electrically operated solenoids control the shifting of all forward gears in the Toyota electronic control four speed automatic transmission. These solenoids are controlled by an ECU which uses throttle position and speed sensor input to determine when the solenoids are turned on. The solenoids normal position is closed, but when it is turned on, it opens to drain fluid from the hydraulic circuit. Solenoid No. 1 controls the 2-3 shift valve. It is located between the manual valve and the top of the 2-3 shift valve. Solenoid No. 2 controls the 1-2 shift valve and the 3-4 shift valve. First Gear During first gear operation, solenoid No. 1 is on and solenoid No. 2 is off. With line pressure drained from the top of the 2-3 shift valve by solenoid No. 1, spring tension at the base of the valve pushes it upward. With the shift valve up, line pressure flows from the manual valve through the 2-3 shift valve and on to the base of the 3-4 shift valve. With solenoid No. 2 off, line pressure pushes the 1-2 shift valve down. In this position, the 1-2 shift valve blocks line pressure from the manual valve. Line pressure and spring tension at the base of the 3-4 shift valve push it upward. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 220. Second Gear During second gear operation, solenoid No. 1 and No. 2 are on. Solenoid No. 1 has the same effect that it had in first gear with the 2-3 shift valve being held up by the spring at its base. Pressure from the manual valve flows through the 2-3 shift valve and holds the 3-4 shift valve up. With solenoid No. 2 on, line pressure from the top of the 1-2 shift valve bleeds through the solenoid. Spring tension at the base of the 1-2 shift valve pushes it upward. Line pressure which was blocked, now is directed to the second brake (132), causing second gean The 3-4 shift valve maintains its position with line pressure from the 2-3 shift valve holding it up. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 221. Third Gear During third gear operation, solenoid No. 1 is off and solenoid No. 2 is on. When solenoid No. 1 is off, it closes its drain and line pressure from the manual valve pushes the 2-3 shift valve down. Line pressure from the manual valve is directed to the direct clutch (C2) and to the base of the 1-2 shift valve. With solenoid No. 2 on, it has the same effect that is had in second gear; pressure is bled at the top of the 1-2 shift valve and spring tension pushes it up. Line pressure is directed to the second brake (B2). However in third gear, the second brake (B2) has no effect since it holds the one-way clutch No. 1 (Fl) and freewheels in the clockwise direction. The second coast brake is ready in the event of a downshift when the OD direct clutch (C2) is released. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 18 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 222. Fourth Gear During fourth gear operation, both solenoids are off. When solenoid No. 1 is off, its operation is the same as in second and third gears. A third solenoid controls lock-up operation. Reprinted with permission by Toyota Motor Sales, USA, Inc., from the Automatic Transmission Course #262 textbook. TOYOTA ELECTRONIC CONTROL TRANSMISSION Page 19 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 223. Checks and Adjustments The transmission requires regular maintenance intervals if it is to continue to operate without failure. As we discussed in previous sections, transmission fluid loses certain properties over time and especially due to heat. The Maintenance Schedules found in the repair manual or the Owners Manual indicate the appropriate replacement schedules based on how the vehicle is used. Schedule A for example, recommends replacement of the fluid every 20,000 miles or 24 months. Whereas Schedule B recommends just an inspection of the fluid every 15,000 miles or 24 months and no replacement interval. The chart below indicates which maintenance schedule to follow based on the use of the vehicle. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 224. Fluid Level The fluid level in the automatic transmission should be inspected by means of the dipstick after the transmission has been warmed up to ordinary operating temperature, approximately 158'F to 176'F. As a rule of thumb, if the graduated end is too hot to hold, the fluid is at operating temperature. The fluid level is proper if it is in the hot range between hot maximum and hot minimum. NOTE: The cool level found on the dip stick should be used as a reference only when the transmission is cold. The correct fluid level can only be found when the fluid is hot. It is important to keep the fluid at the correct level at all times to ensure proper operation of the automatic transmission. If the fluid level is too low, the oil pump will draw in air, causing air to mix with the fluid. Aerated fluid lowers the hydraulic pressure in the hydraulic control system, causing slippage and resulting in damage to clutches and bands. If the fluid level is excessive, planetary gears and other rotating components agitate the fluid, aerating it and causing similar symptoms as too little fluid. In addition, aerated fluid will rise in the case and may leak from the breather plug at the top of the transmission or through the dipstick tube. In addition, be sure to check the differential fluid level in a transaxle. This fluid is sealed off and separate from the transmission cavity in some applications. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 225. Throttle Cable The throttle cable is adjustable on all automatic transmissions. And in each case it controls throttle pressure. Throttle pressure is an indication of load. When the throttle is depressed, the cable transfers this motion to the base of the throttle valve and moves it upward to increase throttle pressure. Throttle pressure causes the primary regulator valve to increase line pressure. As the throttle is depressed, greater torque is produced by the engine and the transmission may also downshift to a lower gear. If line pressure did not increase, slippage could occur which would result in wear of the clutch plate surface material. Throttle pressure's affect on transmission operation differs between a hydraulically controlled transmission (non-ECT) and an electronically controlled transmission (ECT). In a non-ECT transmission, throttle pressure affects shift points and line pressure; whereas in an ECT transmission it only affects line pressure. Control of line pressure will affect the quality of the shift, not the shift points, in an ECT transmission. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 226. Inspect and Adjust the Throttle Cable To inspect the throttle cable adjustment, the engine should be off. Depress the accelerator pedal completely, and make sure that the throttle valve is at the maximum open position. If the throttle valve is not fully open, adjust as needed. With the throttle fully open, check the throttle cable stopper at the boot end and ensure that there is no more than one millimeter between the end of the stopper and the end of the boot. If adjustment is required, make the adjustment with the throttle depressed. Loosen the locking nuts on the cable housing and reposition the cable housing and boot as needed until the specification is reached. The Land Cruiser A440 automatic transmission throttle cable is adjusted differently, as seen below. It is measured in two positions. The first measurement is made with the throttle fully closed. The distance varies in that the measurement is made from the end of the boot to the front of the stopper. Measure the same distance with the throttle in the fully open position. The illustration below represents yet another adjustment type. The rubber boot has a shallow extension when compared to the first one discussed earlier. The procedure differs in that the throttle is left in the fully closed position when the distance is measured from the front of the boot to the front of the stopper. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 227. Inspect and Adjust the Shift Cable To inspect the shift cable, move the gear selector from neutral to each position. The gear selector should move smoothly and accurately to each gear position. Adjust the shift cable in the indicator does not line-up with the position indicator while in the proper detent. To adjust, loosen the swivel nut on the shift linkage. Push the manual lever at the transmission fully toward the torque converter end of the transmission. Then pull the lever back two notches from Park through Reverse to the Neutral position. Set the selector level to the Neutral position and tighten the swivel nut while holding the lever lightly toward the reverse position. Check Idle Speed and Adjust if Applicable Idle speed is an important aspect for transmission engagement. If set too high, when shifting from neutral to drive or reverse, the engagement will be too abrupt, causing not only driver discomfort, but also affecting the components of the transmission as well. And, of course, if the idle is too low, it may cause the engine to stall or idle roughly. To adjust the idle speed: • The engine should be at operating temperature. • All accessories should be off. • Set the parking brake. • Place the transmission in park or neutral position. • Engine cooling fan should be off. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 228. Diagnosis During diagnosis, always verify the customer complaint. If the verification includes a test drive, be sure to check the level of ATF first. This will ensure that a low level is not contributing to the problem and give you an idea as to the condition and service that the vehicle has seen. Although preliminary checks suggest making adjustments, drive the vehicle before any adjustments in order to experience the same condition as the customer. If you are unable to verify the problem, ask the customer to accompany you on the test drive and point-out when the condition occurs. When test driving a vehicle, have a plan and record your findings. The chart that follows is quite thorough and provides room for comments. Rather than trying to remember the results of a specific test, simply refer to the diagnostic form. Not only do you want to find out what has failed, but also what is functioning properly. Armed with this information, you will save time in your diagnosis and be more thorough. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 229. Road Test - Automatic Transmission TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 230. For example, if the transmission does not slip while accelerating from a stop with wide open throttle, line pressure is sufficient. If shift points occur at the proper speeds, throttle pressure and governor pressure are sufficient. Or for ECT transmissions, throttle sensor and speed sensor inputs are being received by the ECU and the circuit and solenoids are working properly. Upshift quality is important to consider during the road test because it is an indicator of proper line pressure and accumulator operation. If all upshifts are harsh, it indicates a common problem such as line pressure and should be verified with a pressure test. If a harsh upshift is evident in a specific gear, check the accumulator which is associated with the holding device for that specific gear. Following the road test, compare your findings with the troubleshooting matrix chart in the repair manual. (An example can be found on page 15.) The matrix chart will assist you in identifying components or circuits which can be repaired while the transmission is mounted in the vehicle. Or identify the components which should be inspected with the transmission on the bench. Based on your diagnosis, if the transmission can be repaired with an on vehicle repair, the off- vehicle repair should be attempted first. Should the transmission require removal from the vehicle, a remanufactured transmission should be evaluated against the cost of an in-house overhaul. Electrical Diagnostic Testing Onboard Diagnostics The ECU is equipped with a built-in self diagnostic system, which monitors the speed sensors, solenoid valves and their electrical circuitry. If the ECU senses a malfunction: 1. It blinks the OD OFF light to warn the driver. 2. It stores the malfunction code in its memory. 3. (When properly accessed) it will output a diagnostic code indicating the faulty component or circuit. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 231. Once a malfunction is stored in the memory system, it will be retained until canceled (erased). The vehicle battery constantly supplies 12 volts to the ECU B terminal to maintain memory even if the ignition switch is turned off. If the malfunction is repaired or returns to normal operation, the warning light will go off but the malfunction code will remain in memory. In order to erase a diagnostic code from the memory, a specified fuse must be removed for approximately 30 seconds with the ignition switch is off. The fuse is identified in the repair manual or on the ECT Diagnostic Information technician reference card. Throttle Position Sensor Signal In order to determine if the throttle position sensor signal and brake switch signal are being received by the ECU, place the ignition switch to the ON position with the engine off, connect a digital voltmeter to the diagnostic check connector and slowly depress the throttle. On models prior to 1987, if the vehicle does not have a diagnostic check connector in the engine compartment, connect the voltmeter to the DG Terminal. Its location can be found in the appropriate repair manual. The ECT terminal can be designated as TT or T1 depending on the vehicle model. The position in the diagnostic check connector remains the same. The voltage will increase in one volt increments from 1 to 8 volts as the throttle is slowly opened. To verify the brake signal, apply the brake pedal while the throttle is wide open. The voltage displayed on the voltmeter screen will go to zero. If the voltage readings progress in a step-like fashion, it indicates proper operation of the following: • Throttle sensor • Circuit integrity from the sensor to the ECU • Circuit integrity from the ECU to the diagnostic check connector. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 232. If the voltage remains at 0 volts as the accelerator is depressed, possible causes are: • Brake signal remains on. • IDL signal remains on. • ECU power supply circuit. • Faulty ECU. The voltage chart above provides a voltage value for the corresponding throttle opening. This can be used to establish accelerator position for a given throttle opening. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 233. Terminal Voltage and Gear Position To check for shift timing while the vehicle is driven, connect a voltmeter and drive the vehicle. Voltage will increase in one volt increments from 0 to 7 volts. These voltage signals are output from the ECU to indicate a response to system sensors. The lock-up voltages in second and third gear may not be consistently output with throttle opening under 50%. In order to output each voltage signal, the throttle will need to be open greater than 50%. If the gears fail to shift in response to the changes in voltage readings, the solenoids may be sticking or the electrical circuit to the solenoid may have an open. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 234. ECT Analyzer The ECT Analyzer is designed to determine if a transmission malfunction is ECU/electrical circuit related or in the transmission. The analyzer is connected at the solenoid electrical connector using appropriate adapter harnesses. The vehicle is driven using the analyzer to shift the transmission. If the transmission operates properly with the ECT Analyzer, the fault lies between the solenoid connectors up to and including the ECU. On the other hand, if the transmission does not operate properly with the analyzer, the fault is likely to be in the transmission. This would include a failure of the solenoid or a mechanical failure of the transmission. A solenoid may test out electrically and fail mechanically because the valve sticks. Apply air pressure to the solenoid; air should escape when the solenoid is energized and should not escape when the solenoid is not energized. Operating Instructions Two technicians are required when testing with the ECT Analyzer. One technician must actually drive the vehicle, and the second technician will change gears. CAUTION The analyzer leads should be routed away from hot or moving engine components to avoid damage to the tester. Choose a safe test area where there are no pedestrians, traffic and obstructions. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 235. Testing for proper gear shifting: 1. The driver and passengers should wear seat belts. 2. Depress the service brake pedal. 3. Start the engine and move the vehicle gear selector to Drive. 4. Rotate the gear selector knob on the ECT Analyzer to the "1-2" position. The transmission will shift to second gear. 5. Press and hold the first gear button. The transmission will shift to first gear. 6. Release the parking brake. 7. Accelerate to 10 mph. 8. Release the first gear button. The transmission should shift to second gear. 9. Accelerate to 20 mph. 10. Rotate the selector knob to the number "T' position. The transmission should shift into third gear. 11. Accelerate to 25 mph. 12. Rotate the selector knob to the number "4" position. The transmission should shift to fourth gear. 13. Release the accelerator and coast. 14. Rotate the selector knob to the number "T' position. The transmission should downshift into third gear. 15. Apply the brakes, and stop the vehicle. Testing is complete. Testing for lockup operation: 1. Operate the vehicle and ECT Analyzer up to fourth gear. 2. Accelerate to 40 mph. 3. Press and hold the "Lockup" button to engage the lockup clutch. Observe the tachometer and note a slight reduction in the engine rpm. (Is more noticeable when the vehicle is going up a slight hill due to converter slippage.) 4. Release the "Lockup" button to disengage the lockup clutch. 5. Apply vehicle brakes, and bring the vehicle to a halt. Test is complete. Note: Testing for lockup can also be performed with the vehicle stopped, but with the engine running, With the gear shift selector in "D," press the "Lockup" button to engage the lockup clutch. With the converter in lockup, the engine idle rpm will drop significantly or stall. If there is no change 'in the engine idle rpm, the lockup function is not operational. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 236. ASSIGNMENT NAME:_______________________________ 1. What components replaced governor and throttle pressure signals in an ECT transmission? 2. How may solenoids are used in a current model ECT transmission. Please state the function (control) of each? 3. Explain the procedure of how to pull and read a transmission trouble code? 4. Explain the procedure of how to separate between a mechanical and/or an electrical problem in an ECT transmission. 5. How many speed sensors are used on a vehicle with an ECT transmission, state location, correct I.D. (name) of each sensor, and which is the primary input to the ECT computer. 6. Explain the procedure for checking ECT speed sensors. 7. Explain the construction and operation of the ECT speed senor. 8. List all inputs used by the ECT computer and the need for each? 9. Explain the construction and operation of the direct TPS (linear) in relationship to an indirect TPS in an ECT transmission? 10.Explain which ECT diagnostic checks can be made from the Diagnostic connector? 11.Explain the conditions that must occur in order for converter lockup to occur in an ECT transmission. 12.Explain the relationship that the brake switch, cruise control, and coolant temperature sensor (THW) have in common with torque converter lockup. 13.Explain how solenoids can be checked on the car. TOYOTA ELECTRONIC TRANSMISSION CHECKS & DIAGNOSIS Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 237. SHIFT INTERLOCK SYSTEM The shift lock system is designed to ensure the proper operation of the automatic transmission. The driver must depress the brake pedal in order to move the gear selector from Park to any other range. In addition, the ignition key cannot be turned to the Lock position and removed from the ignition switch unless the gear selector is placed in the Park position. There are three systems available in Toyota models; electrical, electrical/ mechanical and mechanical. We will not cover the application by model but rather by system type. For the specifics on a particular model, consult the repair manual. SHIFT INTERLOCK SYSTEM Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 238. Electrical Shift Lock Type The electrical type uses electrical control of the shift lock mechanism, as well as the key lock mechanism. Shift Lock Mechanism The shift lock mechanism is made up of a number of components as seen in the illustration below. The shift position switch (shift lock control switch) is used to detect the position of the shift lever. It has two contacts, P1 and P2. When the select lever is in the Park position, P1 is on (closed) and P2 is off (open). In this position, the key can be removed but the select lever is locked in position. When the select lever is in a position other than Park, P1 is off (open) and P2 is on (closed). In this position, the key cannot be removed. The grooved pin is part of the normal detent mechanism which requires that the shift lever button be depressed in order to move the gear selector into and out of Park position and also into Manual 2 or Manual Low positions. The shift lock plate is mounted next to the detent plate. In the Park position, the grooved pin fits into the slot at the top of the shift plate. The shift lock plate movement is limited by the plate stopper when the solenoid is not energized. SHIFT INTERLOCK SYSTEM Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 239. Shift Lock Override Button In order to move the shift lever out of Park, the ignition switch must be in the Accessory or ON position and the brake pedal must be depressed. When the brake pedal is depressed, the ECU turns on the solenoid, moving the plate stopper and allowing the shift lock plate to move down with the grooved pin. If the shift lock solenoid becomes inoperative, the shift lever cannot be moved and the vehicle cannot be moved. The shift lock override button can be used to release the plate stopper from the shift lock plate, releasing the shift lever so it can be moved from the Park position. Shift Lock ECU The ECU is generally found near the shift select lever. The shift lock system computer controls operation of the key lock solenoid and the shift lock solenoid based on signals from the shift position switch and the stop light switch. SHIFT INTERLOCK SYSTEM Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 240. Key Interlock System A camshaft is provided at the end of the key cylinder rotor. This camshaft has a cam with the cut-out portion of its stroke from the ACC position to the ON or Start position. The pin of the key lock solenoid protrudes out against the cam when the current is on and is pulled back by the return spring when the current is off. When the shift lever is shifted to a range other than the P range, current flows from the computer to the key lock solenoid, causing the pin to protrude out. If the key cylinder is turned with the pin in this position, it can be turned to the ACC position but cannot be turned further, due to the pin pushing against the cam. This prevents the key cylinder from being turned to the Lock position. The current to the key lock solenoid is cut off when the shift lever is shifted to the P range and the pin is pulled back by the return spring. This allows the key cylinder to be turned to the Lock position, and the key can be removed. Shift Lock System Computer The shift lock system computer controls operation of the key lock solenoid and the shift lock solenoid based on signals from the shift position switch and the stop fight switch. Key Lock Solenoid Control The shift position switch P2 is on (closed) when the shift lever is in a range other than the Park range. Current from the ACC and ON terminals of the ignition switch flows to Tr2 through the timer circuit. The base circuit of Tr2 is grounded by switch P2, and Tr2 goes on, energizing the key lock solenoid, preventing the key from going to the Lock position. The timer circuit cuts off the flow of current to Tr2 approximately one hour after the ignition switch is turned from ON to ACC, switching off the key lock solenoid. The timer circuit prevents the battery from being discharged. By placing the gear selector in the Park position, switch P2 is off (open), current no longer flows to the base of Tr2 and it goes off. The solenoid is no longer energized, and the solenoid plunger is retracted, and the key can be removed. SHIFT INTERLOCK SYSTEM Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 241. Shift Lock Solenoid Control When the shift lever is in the Park range, shift position switch P1 is on and the emitter circuit of Tr3 is grounded. Base current for Tr3 is provided through the stop light switch which is open while the brake is not applied, so Tr3 is off. Tr3 controls the base of Tr1, and as long as Tr3 is off, the shift lock solenoid will remain off and the gear selector will be locked in the Park position. When the brake pedal is depressed, the stop light switch goes on, providing current to the base of Tr3. When Tr3 goes on, base current flows in Tr1 and it then goes on, causing current to flow to the shift lock solenoid and freeing the shift lever. When the shift lever is shifted out of Park, the shift position switch P1 goes off and Tr1 switches the shift lock solenoid off. SHIFT INTERLOCK SYSTEM Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 242. Electrical / Mechanical Shift Lock Type The electrical/mechanical type uses electrical control of the shift lock mechanism and a mechanical control of the key lock mechanism. Key Interlock Device Similar to the construction discussed previously, a camshaft is provided at the end of the key cylinder rotor. This camshaft has a cam with the cut-out portion of its stroke from the ACC position to the ON or Start position. The lock pin is attached to the end of the parking lock cable and slides with the movement of the control lever mounted to the shift lever mechanism. The control lever is separate from the shift lock plate but is actuated by it. Notice the crank ditch sloth in the shift lock plate. It is cut at an angle so that when the shift lock plate moves up or down, it causes the control lever to pivot at point B in the illustration below. When the shift lever is in the Park position, the control lever rotates around B counterclockwise, pushing the parking lock cable so that the lock pin does not interfere with the camshaft. In this position, the key can be turned to the Lock position and removed. When the shift lever is moved from the Park position, the lock plate is pushed downward by the shift lever button and the grooved pin. When the shift lock plate moves downward the control lever rotates clockwise, pulling the parking lock cable and lock pin into engagement with the camshaft. In this position, the key cannot be turned to the Lock position and removed from the ignition as seen in the following illustration. SHIFT INTERLOCK SYSTEM Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 243. Mechanical Shift Lock Type The mechanical type uses mechanical control of the shift lock mechanism and the key lock mechanism. A cable extends from the brake pedal bracket to the shift lever control shaft bracket. A lock pin engages the shift lever shaft to lock in into the Park position until the brakes are applied. The cable (wire) end on the brake pedal bracket is mounted just below the stop light switch. The plunger is attached to the cable and is mounted in a wire guide and is able to slide in and out. When the brake pedal is not depressed, the plunger is held in position by the brake pedal return spring. The other end of the cable is attached to a lock pin located in the shift lever control shaft bracket. The lock pin is spring loaded to release the lock pin from the inner shaft of the shift lever. SHIFT INTERLOCK SYSTEM Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 244. When the shift lever is in the Park range and brakes are not applied, the cable compresses the No. 1 return spring and pushes the lock pin engaging the round hole in the inner shaft, locking the shift lever in Park When the brakes are applied with the transmission in Park, the No. 1 spring pushes the cable, lock pin and plunger out toward the brake pedal. With the plunger released, the shift lever can be moved from Park. When the shift lever is in positions other than Park with the brakes released, the brake pedal return spring pushes the plunger and cable back toward the shift lever control shaft. The lock pin cannot enter the inner shaft, so the No. 2 return spring compresses. With the lock pin spring loaded, when the gear selector is moved to the Park position, it will immediately lock. Reprinted with permission by Toyota Motor Sales, USA, Inc., from the Automatic Transmission Course #262 textbook. SHIFT INTERLOCK SYSTEM Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 245. Electronic Fuel Injection Overview How Electronic Fuel Injection Works Electronic Fuel injection works on the some very basic principles. The following discussion broadly outlines how a basic or Convention Electronic Fuel Injection (EFI) system operates. The Electronic Fuel Injection system can be divided into three: basic sub-systems. These are the fuel delivery system, air induction system, and the electronic control system. EFI #1 - SYSTEM OVERVIEW Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 246. The Fuel Delivery System • The fuel delivery system consists of the fuel tank, fuel pump, fuel filter, fuel delivery pipe (fuel rail), fuel injector, fuel pressure regulator, and fuel return pipe. • Fuel is delivered from the tank to the injector by means of an electric fuel pump. The pump is typically located in or near the fuel tank. Contaminants are filtered out by a high capacity in line fuel filter. • Fuel is maintained at a constant pressure by means of a fuel pressure regulator. Any fuel which is not delivered to the intake manifold by the injector is returned to the tank through a fuel return pipe. EFI #1 - SYSTEM OVERVIEW Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 247. The Air Induction System • The air induction system consists of the air cleaner, air flow meter, throttle valve, air intake chamber, intake manifold runner, and intake valve. • When the throttle valve is opened, air flows through the air cleaner, through the air flow meter (on L type systems), past the throttle valve, and through a well tuned intake manifold runner to the intake valve. • Air delivered to the engine is a function of driver demand. As the throttle valve is opened further, more air is allowed to enter the engine cylinders. • Toyota engines use two different methods to measure intake air volume. The L type EFI system measures air flow directly by using an air flow meter. The D type EFI system measures air flow indirectly by monitoring the pressure in the intake manifold. EFI #1 - SYSTEM OVERVIEW Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 248. Electronic Control System • The electronic control system consists of various engine sensors, Electronic Control Unit (ECU), fuel injector assemblies, and related wiring. • The ECU determines precisely how much fuel needs to be delivered by the injector by monitoring the engine sensors. • The ECU turns the injectors on for a precise amount of time, referred to as injection pulse width or injection duration, to deliver the proper air/fuel ratio to the engine. EFI #1 - SYSTEM OVERVIEW Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 249. Basic System Operation • Air enters the engine through the air induction system where it is measured by the air flow meter. As the air flows into the cylinder, fuel is mixed into the air by the fuel injector. • Fuel injectors are arranged in the intake manifold behind each intake valve. The injectors are electrical solenoids which are operated by the ECU. • The ECU pulses the injector by switching the injector ground circuit on and off. • When the injector is turned on, it opens, spraying atomized fuel at the back side of the intake valve. • As fuel is sprayed into the intake airstream, it mixes with the incoming air and vaporizes due to the low pressures in the intake manifold. The ECU signals the injector to deliver just enough fuel to achieve an ideal air/fuel ratio of 14.7:1, often referred to as stoichiometry. • The precise amount of fuel delivered to the engine is a function of ECU control. • The ECU determines the basic injection quantity based upon measured intake air volume and engine rpm. • Depending on engine operating conditions, injection quantity will vary. The ECU monitors variables such as coolant temperature, engine speed, throttle angle, and exhaust oxygen content and makes injection corrections which determine final injection quantity. EFI #1 - SYSTEM OVERVIEW Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 250. Advantages of EFI Uniform Air/Fuel Mixture Distribution Each cylinder has its own injector which delivers fuel directly to the intake valve. This eliminates the need for fuel to travel through the intake manifold, improving cylinder to cylinder distribution. Highly Accurate Air/Fuel Ratio Control Throughout All Engine Operating Conditions EFI supplies a continuously accurate air/fuel ratio to the engine no matter what operating conditions are encountered. This provides better driveability, fuel economy, and emissions control. Superior Throttle Response and Power By delivering fuel directly at the back of the intake valve, the intake manifold design can be optimized to improve air velocity at the intake valve. This improves torque and throttle response. Excellent Fuel Economy With Improved Emissions Control Cold engine and wide open throttle enrichment can be reduced with an EFI engine because fuel puddling in the intake manifold is not a problem. This results in better overall fuel economy and improved emissions control. Improved Cold Engine Startability and Operation The combination of better fuel atomization and injection directly at the intake valve improves ability to start and run a cold engine. Simpler Mechanics, Reduced Adjustment Sensitivity The EFI system does not rely on any major adjustments for cold enrichment or fuel metering. Because the system is mechanically simple, maintenance requirements are reduced. EFI #1 - SYSTEM OVERVIEW Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 251. EFI #1 - SYSTEM OVERVIEW Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 252. EFI/TCCS System With the introduction of the Toyota Computer Control System (TCCS), the EFI system went from a simple fuel control system to a fully integrated engine and emissions management system. Although the fuel delivery system operates the same as Conventional EFI, the Ignition Spark Management (ESA) The EFI/'TCCS system regulates spark advance angle by monitoring engine operating conditions, calculating the optimum spark timing, and firing the spark plug at the appropriate time. Idle Speed Control (ISC) The EFI/TCCS system regulates engine idle speed by means of several different types of ECU controlled devices. The ECU monitors engine operating conditions to determine which idle speed strategy to use. TCCS Electronic Control Unit (ECU) also controls ignition spark angle. Additionally, TCCS also regulates an Idle Speed Control device, an Exhaust Gas Recirculation (EGR) Vacuum Switching Valve and, depending on application, other engine related systems. Exhaust Gas Recirculation (EGR) The EFI/TCCS system regulates the periods under which EGR can be introduced to the engine. This control is accomplished through the use of an EGR Vacuum Switching Valve. Other Engine Related Systems In addition to the major systems just described, the TCCS ECU often operates an Electronically Controlled Transmission (ECT), a Variable Induction System (T-VIS), the air conditioner compressor clutch, and the turbocharger/supercharger. EFI #1 - SYSTEM OVERVIEW Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 253. Self Diagnosis System A self diagnosis system is incorporated into all TCCS Electronic Control Units (ECUs) and into some Conventional EFI system ECUs. A Conventional EFI engine equipped with self diagnostics is a P7/EFI system. This diagnostic system uses a check engine warning lamp in the combination meter which is capable of warning the driver when specific faults are detected in the engine control system. The check engine light is also capable of flashing a series of diagnosis codes to assist the technician in troubleshooting these faults. Summary The Electronic Fuel Injection system consists of three basic subsystems. • The electronic control system determines basic injection quantity based upon electrical signals from the air flow meter and engine rpm. • The fuel delivery system maintains a constant fuel pressure on the injector. This allows the ECU to control the fuel injection duration and deliver the appropriate amount of fuel for engine operating conditions. • The air induction system delivers air to the engine based on driver demand. The air/fuel mixture is formed in the intake manifold as air moves through the intake runners. The EFI system allows for improved engine performance, better fuel economy, and improved emissions control. Although technologically advanced, the EFI system is mechanically simpler than other fuel metering systems and requires very little maintenance or periodic adjustment. • The Conventional EFI system only controls fuel delivery and injection quantity. 'Me introduction of EFI/TCCS added control Of Electronic Spark Advance, idle speed, EGR, and other related engine systems. • Most of Toyota's late model EFI systems are equipped with some type of on board diagnosis system. All TCCS systems are equipped with an advanced self diagnosis system capable of monitoring many important engine electrical circuits. Only some of the later production Conventional(P7) EFI engines are equipped with a self diagnosis system. Reprinted with permission from Toyota Motor Sale, U.S.A., Inc. from #850 EFI Course Book. EFI #1 - SYSTEM OVERVIEW Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 254. Overview Of The Air Induction System The purpose of the air induction system is to filter, meter, and measure intake air flow into the engine. Air, filtered by the air cleaner, passes into the intake manifold in varying volumes. The amount of air entering the engine is a function of throttle valve opening angle and engine rpm. Air velocity is increased as it passes through the long, narrow intake manifold runners, resulting in improved engine volumetric efficiency. Intake air volume is measured by movement of the air flow meter measuring plate or by detecting vortex frequency on engines equipped with L type EFI. On engines equipped with D type EFI, air volume is measured by monitoring the pressure in the intake manifold, a value which varies proportionally with the volume of air entering the engine. The throttle valve directly controls the volume of air which enters the engine based on driver demand. Additionally, when the engine is cold, it is necessary for supplementary air to by-pass the closed throttle valve to provide cold fast idle. This is accomplished by a bi- metallic or wax type air valve or by an ECU controlled Idle Speed Control Valve (ISCV). EFI #2 - AIR INDUCTION SYSTEM Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 255. Air Induction System Components Vane Air Flow Meter (L Type EFI) The vane type air flow meter is a commonly used air volume measurement device on Toyota EFI engines. The meter consists of a measuring plate, which is spring loaded closed by a return spring, and a potentiometer attached to the plate, which varies an electrical signal to the ECU as the position of the plate changes. Air volume entering the engine is directly proportional to the amount of movement detected from the measuring plate. Additionally, the air flow meter incorporates a fuel pump enable contact which breaks the ground circuit of the circuit opening relay if the engine stops running. The air flow meter is placed in series between the air cleaner and the throttle body, thereby measuring all air which enters the engine. Integrated with the air flow meter is an intake air temperature sensor and an idle mixture by-pass passage. Idle Mixture Air By-pass Circuit For proper calibration of the engine air/fuel ratio at idle speed, an idle mixture air by-pass circuit is incorporated into the air flow meter. A screw is used to adjust the amount of air which by-passes the measuring plate. This screw is adjusted and sealed at the factory to discourage improper adjustment and tampering. There are no provisions or specifications for field adjustment. After factory calibration of the air flow meter, a two-digit number is stamped into the meter casting near the idle mixture adjusting screw. This number indicates the distance from the casting to the flat surface of the screw and can be used as a reference if the idle mixture screw has been tampered with. The calibration number can be interpreted by referring to the examples in the following chart. EFI #2 - AIR INDUCTION SYSTEM Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 256. Fuel Pump Circuit Control A fuel pump switch is incorporated into the air flow meter to prevent the fuel pump from running unless the engine is running. Any movement of the air flow meter measuring plate will cause the fuel pump switch contact to close. When the engine is not running, the measuring plate forces the fuel pump switch contact open, preventing the circuit opening relay from operating. For more information on the fuel pump electrical circuit, refer to section 3, "Fuel Delivery and Injection Control." Karman Vortex Air Flow Meter (L Type EFI) The Karman vortex air flow meter is used only on limited applications (7M-GTE and Lexus 1UZ-FE & 2JZ-GE engines). The meter is smaller and lighter than the vane type meter and offers less resistance to incoming air flow. The sensor operates on the principle of measuring the vortices created as air flows past a pillar shaped vortex generator. The frequency with which these vortices are created increases in direct proportion to the amount of air flowing across the vortex generator. Vortex frequency is detected by a photocoupler and converted into a variable frequency digital signal by the sensor. An intake air temperature sensor is also incorporated into the Karman vortex air flow meter. For more information about operation of this air flow meter and its signals , refer to section 5, "Electronic Engine Controls." Throttle Body The throttle body consists of the throttle valve, the idle air by-pass circuit, the throttle position sensor, and also houses various ported and manifold vacuum sources to operate emissions devices. Throttle icing is prevented by use of an engine coolant cavity located adjacent to the throttle valve. EFI #2 - AIR INDUCTION SYSTEM Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 257. Idle Air By-pass During idle operation, the throttle valve is almost completely closed. Idle air enters the engine through an adjustable throttle air by- pass screw which varies the amount of air which can flow past the closed throttle valve. By turning this screw clockwise, throttle bypass air is reduced, causing a decrease in idle speed. Conversely, turning the screw counterclockwise will increase idle speed by allowing more air to pass the closed throttle valve. On engines equipped with an ECU controlled ISCV, this throttle air by-pass screw is seated at the factory, and there are no provisions for curb idle adjustment. Idle air is varied by the ECU through control of the ISC Valve position. Decel Dashpot and Throttle Opener Systems A decel dashpot or throttle opener is mounted to the throttle body on some engines. The decel dashpot is designed to keep the throttle valve from closing too suddenly during deceleration. The throttle opener is designed to hold the throttle valve open slightly after the engine is turned off. Non ECU Controlled Throttle Opener Starting with 1990 3S-FE and 5S-FE engines, a simple throttle opener diaphragm was added to the throttle body. The throttle opener diaphragm is spring loaded in the extended position, holding the throttle valve open slightly when vacuum is not applied to the diaphragm. When the engine is started, manifold vacuum from the TO port retracts the throttle opener for normal curb idle. The intent of the throttle opener system is to keep the throttle valve slightly open after the engine is turned off. Non-ECU Controlled Dashpot On some engines, a simple dashpot is used. When the throttle is open, the dashpot diaphragm spring extends the control rod, allowing atmospheric pressure to enter the diaphragm chamber through a small bleed restriction (VTV). EFI #2 - AIR INDUCTION SYSTEM Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 258. When the throttle closes, the throttle return spring pushes the dashpot control rod toward the retracted position. Atmospheric pressure trapped in the diaphragm chamber slowly bleeds through the restriction, causing the throttle to close slowly. ECU Controlled Combination Throttle Opener/Dashpot Dashpot and throttle opener functions are combined into one ECU controlled system on some late model engines like the '91 3E- E. This system uses an ECU controlled VSV to switch vacuum to the throttle opener/dashpot diaphragm. • When the engine is stopped, spring tension extends the control rod, causing the throttle to open. • When the engine is running above a given rpm, the ECU energizes the VSV, allowing atmospheric pressure to bleed into the throttle opener/dashpot diaphragm through the Vacuum Transmitting Valve (VTV). This allows spring tension to extend the control rod. • When the throttle angle closes beyond a specified point during deceleration, the ECU de-energizes the VSV, allowing manifold vacuum to bleed through the VTV and act on the diaphragm. This causes the control rod to gradually retract, slowly closing the throttle valve. The idle air by-pass screw, dashpot, and throttle opener do not require routine adjustment. In the event that these components have been tampered with, refer to the appropriate repair manual for adjustment procedures of curb idle, dashpot, throttle opener, and A/C idle up. • ECU turns VSV ON as throttle opens; rod extends • ECU turns VSV OFF on deceleration; rod allows throttle to close slowly • Engine OFF; rod extends, holding throttle open slightly EFI #2 - AIR INDUCTION SYSTEM Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 259. Air Valves There are two types of non-ECU controlled air valves used on some engines to control cold engine fast idle. These valves, the electrically heated bi-metal type and the coolant heated wax type, vary the amount of air bypassing the closed throttle valve during cold engine operation. Bi-metal Type Air Valve This gate valve operates on the principle of a spring loaded gate balanced against a bi- metal element. The tension of the bi-metallic element varies the position of the gate as its temperature changes. The bi-metal element is heated by an electrical heater coil and by the temperature of the ambient air surrounding it. The air valve assembly is installed on the surface of the cylinder head to keep the gate valve closed during hot soak periods. EFI #2 - AIR INDUCTION SYSTEM Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 260. Heater current for the air valve is supplied by the circuit opening relay power contact, the same circuit which feeds the fuel pump. Air valve operation can be quick checked by pinching off a supply hose and observing the rpm drop. When checked with a warm engine, the drop should be less than 50 rpm. When the engine is cold, the rpm drop should be high. EFI #2 - AIR INDUCTION SYSTEM Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 261. Wax Type Air Valve The wax type air valve is integrated with the throttle body and varies an idle air by-pass opening as coolant temperature changes. The valve works on the principle of a spring loaded gate valve balanced against a coolant heated, wax filled thermo valve. When coolant temperature is cold, the wax filled thermo valve retracts allowing spring A to push the gate valve open. This allows air to flow from the air cleaner side of the valve to the intake side of the valve. As coolant temperature rises, the wax filled thermo valve expands allowing spring B to gradually close the valve (spring B is stronger than spring A). This causes engine rpm to decrease as air flow to the intake is decreased. The wax type air valve should be fully closed by the time engine coolant temperature reaches approximately 80'C (176'F). • Cold engine, large rpm drop • Fully warmed engine!~100 rpm drop EFI #2 - AIR INDUCTION SYSTEM Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 262. A good quick check for the wax type air valve is to observe engine rpm throughout the warm up cycle. Look for high rpm upon initial startup and gradual reduction to normal curb idle speed as the engine reaches normal operating temperature. On D type EFI, the valve operation can also be checked by removing the air inlet pipe at the throttle body and blocking the fresh air port inside the throttle bore. When the engine is cold, engine rpm should drop greater than 100 rpm. Once the engine reaches normal operating temperature (~~ 176'F), rpm drop should not exceed 100 rpm. Intake Air Chamber & Manifold Port delivered Electronic Fuel Injection systems offer the advantage of not having to move fuel through the intake manifold. This allows for improved performance and emissions through optimum design of the intake air chamber and manifolds. A large intake air chamber is provided to eliminate pulsation, thereby improving air distribution to each manifold runner. Long, narrow manifold runners are branched off to each intake port to improve air velocity at the intake valve. This design offers the following benefits: • Fuel puddling is eliminated, providing for leaner cold engine and power air/fuel ratios. This equates to reductions in emissions and improved fuel economy. • Volumetric efficiency of the engine is improved, thereby improving engine torque and horsepower. Depending upon application, the intake air chamber and manifolds may be integrated or separate. Some Toyota engines utilize an ECU controlled variable induction system which optimizes manifold design for low and high speed engine operation. For more information on these systems, refer to "Other TCCS Related Systems." EFI #2 - AIR INDUCTION SYSTEM Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 263. Manifold Absolute Pressure Sensor (D Type EFI) The D type EFI system eliminates the use of an air flow meter and uses a manifold absolute pressure sensor as a load measurement device instead. Because pressure in the intake manifold is proportional to the amount of air entering it, the manifold absolute pressure sensor is used to measure air intake volume in the D type EFI system. This sensor compares a variable pressure inside the intake manifold with a fixed reference pressure inside the sensor. A total vacuum chamber is placed on one side of a piezo-resistive silicon chip; manifold pressure is applied to the other side of the chip. As the chip flexes, the mechanical movement is converted into a variable voltage signal by the sensor. There are several different names used in reference to the Manifold Absolute Pressure sensor, depending on the publication you read. Two other common names used to refer to this sensor are PIM, or Pressure Intake Manifold, and Vacuum sensor. For more information about operation of the manifold absolute pressure sensor and its signal characteristics, refer to "Electronic Engine Controls." EFI #2 - AIR INDUCTION SYSTEM Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 264. Idle-Up Systems Air Conditioning Idle-up The air conditioning idle-up system is used to increase engine idle rpm any time the air conditioning compressor is in operation. The system shown is used on D type EFI applications where the ECU controlled Idle Speed Control Valve (ISCV) does not have an A/C idle-up feature. This system maintains engine idle stability during periods of A/C compressor operation. Additionally, it keeps compressor speed sufficiently high to ensure adequate cooling capacity at idle speed. The A/C idle-up system consists of an A/C amplifier controlled Vacuum Switching Valve (VSV) and an Air Switching Valve (ASV) or actuator. By applying vacuum to the ASV diaphragm, fresh air from the air cleaner is by-passed into the intake manifold, increasing engine rpm. When the VSV is energized, a manifold vacuum signal is applied to the actuator diaphragm of the ASV causing it to open the passage between the fresh air supply and the intake manifold. This extra air introduced directly into the intake manifold causes engine rpm to increase. When the VSV is de-energized, the vacuum control signal to the ASV is blocked and any trapped vacuum is bled off of the diaphragm. This causes the ASV to block air flowing to the intake manifold, decreasing rpm. The A/C idle-up system described above is not an ECU controlled system. For information on ECU controlled ISCV systems which control A/C idle-up speed, refer to "Engine Controls - Idle Speed Control Systems." EFI #2 - AIR INDUCTION SYSTEM Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 265. Power Steering Idle-up The power steering system draws a significant amount of horsepower from the engine when the steering wheel is turned to either stop. This can have an adverse effect on vehicle driveability. To address this potential problem, many EFI engines equipped with power steering use a power steering idle-up system which activates whenever the steering wheel is turned to a stop. The power steering idle-up system consists of a hydraulically operated air control valve and a vacuum circuit which by-passes the throttle valve. Whenever power steering pressure exceeds the calibration point of the control valve, the valve opens, allowing a calibrated volume of air to by-pass the closed throttle valve. Because power steering pressure only exceeds the pressure calibration point of the valve when the steering wheel is turned to its stop, the system is only functional during very low speed maneuvering and at idle. The system can be tested by turning the steering wheel to a stop while listening for an rpm increase. EFI #2 - AIR INDUCTION SYSTEM Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 266. Common Service Concerns and Solutions During service procedures, there are two concerns related to the air induction system which the technician should be aware of. These are false or unmeasured air entry into the intake system and deposit buildup on the back side of intake valves. False air is any air which enters the induction system unwanted and/or unmeasured. In addition to obvious leaks in the intake manifold, with an L type EFI system, false air can enter the induction system through the connecting pipe between the air flow meter and the throttle body as well as through leaks into the crankcase. Because this air is able to enter the intake manifold unmeasured, the result is an excessively lean air/fuel ratio. The end result of false air with L type EFI is rough idle, stumble, and/or flat spots. With the D type EFI system, false air is typically measured by the EFI system because it results in an increase in manifold absolute pressure. The end result is an engine that idles excessively high but with a relatively normal air/fuel mixture. There are several tests which can detect false air entry into the induction system. A good visual inspection of the intake air connector pipe and connection points as well as inspection of all vacuum hoses, engine oil filler cap, and dip stick seals are a must. If this fails to identify a suspected leak, spraying carburetor cleaner around suspected leak areas while observing an infrared exhaust analyzer for carbon monoxide increase is another method to assist in leak detection. Another method to locate suspected false air entry points is to pressurize the intake system with a regulated shop air supply (CAUTION: do not exceed 25 PSI). Spray a soapy water solution around all suspected leak areas. Simply listen and observe for bubbles to locate leak sources. This method requires sealing the air cleaner fresh air inlet and blocking the throttle valve open to pressurize the intake air connector pipe. The air pressure can be applied through any large manifold vacuum fitting. EFI #2 - AIR INDUCTION SYSTEM Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 267. This condition manifests itself as hardened carbon deposits on the back side of the intake valves. It varies in degree depending on the engine, fuel quality, and customer driving habits. Intake valve deposits present a dual problem. First, these deposits restrict the flow of air and fuel mixture into the cylinder, reducing volumetric efficiency and potentially affecting high rpm engine performance. Additionally, these carbon deposits act like sponges absorbing fuel vapor. This causes lean driveability problems, particularly during cold engine operation. The best way to identify this condition is by symptom and then through visual inspection. A visual inspection can be performed using a borescope, SSI #00451-42889, to confirm the problem. The intake manifold can also be removed to confirm the existence and the degree of this condition. The accompanying chart will help you to determine the appropriate action to take based upon visual inspection. Visual inspection can be performed without removal of the cylinder head or intake manifold by using a borescope, SSI 00451-42889. The engine can be manually rotated until the intake valve is fully open; then the borescope can be inserted through a spark plug hole for inspection. Repairs can be affected by use of SST 00002216401, a walnut shell type Carbon Cleaner Kit, and 00002-217256, a Universal Plate & Gasket Kit. These tools will allow removal of deposits without removal of the cylinder head. Summary In this chapter, you have learned that the air induction system filters, meters, and measures air flow into the engine. By using multiple port injection, the intake system can be designed with long tuned intake runners to improve the engine's volumetric efficiency. Air flow into the engine is controlled by the driver by opening and closing the throttle valve. As air enters the engine, it is measured by one of three different types of air flow meters with L type injection or by a manifold absolute pressure sensor with D type injection. To improve engine idle quality during cold engine operation, some engines use a mechanical air valve to control air flow past the closed throttle valve. There are two different types of air valves used, one heated by engine coolant, the other heated electrically. Depending on engine application, there are several different types of throttle control and idle-up devices used. Throttle body mounted devices provide a deceleration dashpot function and/or throttle opener function. Remotely mounted idle-up devices are used on some engines to control additional air flow into the engine when load from the A/C compressor or power steering pump are placed on the engine. In section 3, Fuel Deliver & Injection controls, you will learn about the fuel delivery system. EFI #2 - AIR INDUCTION SYSTEM Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 268. Reprinted with permission from Toyota Motor Sale, U.S.A., Inc. from #850 EFI Course Book. EFI #2 - AIR INDUCTION SYSTEM Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 269. Overview of the Fuel Delivery System The fuel delivery system incorporates the following components: 1) Fuel tank (with evaporative emissions controls) 2) Fuel pump 3) Fuel pipe and in line filter 4) Fuel delivery pipe (fuel rail) 5) Pulsation damper (many engines) 6) Fuel injectors 7) Cold start injector (most engines) 8) Fuel pressure regulator 9) Fuel return pipe Fuel is pumped from the tank by an electric fuel pump, which is controlled by the circuit opening relay. Fuel flows through the fuel filter to the fuel rail (fuel delivery pipe) and up to the pressure regulator where it is held under pressure. The pressure regulator maintains fuel pressure in the rail at a specified value above intake manifold pressure. This maintains a constant pressure drop across the fuel injectors regardless of engine load. Fuel in excess of that consumed by engine operation is returned to the tank by way of the fuel return line. A pulsation damper, mounted to the fuel rail, is used on some engines to absorb pressure variations in the fuel rail due to injectors opening and closing. The fuel injectors, which directly control fuel metering to the intake manifold, are pulsed by the ECU. The ECU completes the injector ground circuit for a calculated amount of time referred to as injection duration or injection pulse width. The ECU determines which air/fuel ratio the engine runs at based upon engine conditions monitored by input sensors and a program stored in its memory. During cold engine starting, many engines incorporate a cold start injector designed to improve startability below a specified coolant temperature. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 270. Fuel Delivery and Injection Control Components Fuel Pumps Over the years, Toyota has used two types of electric fuel pumps on EFI systems. The early Conventional EFI system used an externally mounted in-line pump. These roller cell pumps incorporate an integral pressure pulse damper or silencer designed to smooth out pressure pulses and provide quiet operation. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 271. Later model production engines utilize an in- tank pump integrated with the fuel sender unit. These turbine pumps operate with less discharge pulsation and run quieter than the in-line variety. In-tank pumps can be serviced by removing the fuel sender unit from the tank. Make sure that the pump coupling hose is in good condition prior to replacing the pump. Both pumps share many features. They are referred to as wet pumps because the electric motor operates immersed in fuel. Passing fuel through the pump motor aids in cooling and lubrication. An outlet check valve is incorporated in the discharge outlet to maintain residual or rest pressure when the engine is turned off. This reduces the possibility of vapor-lock and improves starting characteristics. A pressure relief valve is used to prevent over-pressure and potential fuel leakage in the event that pressure or return lines become restricted. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 272. Fuel Pump Electrical Controls and Circuit Opening Relay Circuit Opening Relay Circuits There are three types of fuel pump control circuits used on Toyota's EFI engines. One type of control, A second type of fuel pump control uses the ECU to control circuit opening relay run winding current. Used on engines equipped with D type EFI and on the 7M-GTE, which uses a Karman vortex air flow meter, this used exclusively with L type injection, utilizes the air flow meter Fc contact to complete the circuit opening relay run winding ground. This is a safety feature which prevents the fuel pump from operating when the engine is not running. safety feature prevents fuel pump operation whenever the ECU fails to see an Ne (engine rpm) signal. Under these conditions, the ECU removes ground from the circuit opening relay run winding. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 273. Fuel Pump Speed Control The third type of fuel pump control circuit utilizes a two-speed pump electrical circuit. Depending upon engine, the circuit opening relay may be driven by the ECU or by the air flow meter Fc contact. Pump current, however, is supplied either through a current limiting resistor or directly to the pump depending on engine load, rpm and status of the STA signal. When the engine is cranked, or operated at high speed and/or heavy load, the ECU turns off TR1, closing contact A of the Fuel Pump Control Relay. This allows current to flow directly to the fuel pump, causing it to run at high speed. Under all other operating conditions, the ECU turns on TR1, which energizes the Fuel Pump Control Relay. This closes relay contact B and forces current to flow through the resistor, causing the pump to run at low speed. The Fuel Pump Speed Control system is designed to reduce electrical demand and pump wear when fuel demand is low while delivering adequate fuel volume when demand is high. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 274. Fuel Pump Test Terminals To facilitate testing and allow pump operation independent of the air flow meter or ECU control, all engines utilize a fuel pump test connector. There are two basic types of fuel pump test circuits. Most late model TCCS engines use an Fp test terminal located in the check connector. With the ignition switch on, jumpering +B to the Fp terminal sends current-directly to the fuel pump. Earlier engines use a jumper connector referred to as a 2P fuel pump check connector. This connector, when jumpered, supplies ground for the circuit opening relay run winding, allowing it to operate independently of the air flow meter Fc contact. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 275. Fuel Filter The fuel filter, which is installed between the pump and the fuel rail, removes dirt and contaminants from the fuel before it is delivered to the injectors and pressure regulator. Although it is possible for the fuel filter to become contaminated or even completely clogged, this is an unlikely condition because of the high capacity and quality of Toyota's filter. This filter is considered to be maintenance free and no service interval is recommended for periodic replacement. In the event that this filter becomes restrictive to fuel flow, the engine will suffer from surging, loss of power under load and hard starting problems. If it becomes necessary to replace this filter there are some important safety matters to consider. Fuel Delivery Pipe (Fuel Rail) The fuel delivery pipe, commonly referred to as a fuel rail, is designed to hold the injector in place on the intake manifold. Mounted to the fuel delivery pipe are the pulsation damper (when used) and the fuel pressure regulator. The fuel delivery pipe acts as a reservoir for fuel which is held under pressure prior to delivery by the fuel injector. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 276. Fuel Pressure Regulator The fuel pressure regulator is a diaphragm operated pressure relief valve. To maintain precise fuel metering, the fuel pressure regulator maintains a constant pressure differential across the fuel injector. This means that the pressure in the fuel rail will always be at a constant value above manifold absolute pressure. The specified pressure differential is either 36 PSI (2.55 kg/CM2) or 41 PSI (2.90 kg/CM2) depending on engine application.* Maintenance of this pressure differential is accomplished by balancing a spring, assisted by manifold pressure, against a diaphragm which holds a ball valve on its seat. Pulsation Damper Although fuel pressure is maintained at a constant value by the pressure regulator, the pulsing of the injectors causes minor fluctuations in rail pressure. The pulsation damper acts as an accumulator to smooth out these pulsations, ensuring accurate fuel metering. The fuel pulsation damper is not used on all engines but can be used as a fuel pressure quick check on those engines which it is used. Noting the diaphragm, when pressure is present, the bolt head in the center of the diaphragm extends out flush with the top of the damper case. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 277. Fuel Pressure Up System The fuel pressure up system (FPU) is designed to reduce the possibility of vapor formation in the fuel rail after hot soak and is used on many TCCS engines. It utilizes an ECU controlled Vacuum Switching Valve (VSV) to open an atmospheric bleed into the manifold reference line to the fuel pressure regulator. This solenoid is energized during hot engine cranking and for up to two minutes after the engine starts. The ECU grounds the FPU VSV based on input received from STA and THW signals. Energizing the solenoid bleeds atmospheric pressure into the fuel pressure regulator vacuum chamber increasing fuel rail pressure to its maximum level. On some engines, the ECU also monitors engine load and rpm signals (Vs, PIM and Ne) and energizes the VSV under heavy load and high rpm operation to ensure maximum fuel rail pressure. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 278. Fuel Pressure and Volume Testing Safety Tips: Prior to installing a fuel pressure gauge and checking fuel pressure, residual pressure must be safely relieved to reduce the hazard of fire when the fuel line is opened. It is advisable to have a fire extinguisher whenever opening the fuel system. Common gauge hookup locations are at the fuel rail, fuel filter, or the cold start valve using SST #09268-45012 and #09268-45013-01. Repair manual procedures should always be followed. Whenever a fuel hose connection secured with a copper sealing gasket is opened, a new gasket should be used when the hose is re-secured after service. Fuel pressure and volume tests can be divided into six separate areas. The following tests and specifications are general guidelines; consult the repair manual for actual specifications and procedures. CAUTION: Perform this test only long enough to determine if pressure rises above minimum specification; risk exists of blowing coupler hose off of pump. This test is only necessary if other pressure tests indicate lower than normal fuel pressure. Fuel Injectors The fuel injector is an electro-mechanical device which meters, atomizes and directs fuel into the intake manifold based on signals from the ECU driver circuit(s). All Toyota engines used in the U.S.A. position the injectors, one per cylinder, directly behind the intake valve. The injectors are installed with an insulator/seal on the manifold end to isolate the injector from heat and to prevent an atmospheric pressure leak into the manifold. The fuel delivery pipe serves to secure the injector in place. Fuel is sealed on the delivery pipe end by an O-ring and grommet. To reduce the possibility of vapor lock, which tends to occur during high temperature operation, the 3S-GTE and 2TZ-FE engines use a side feed injector. This type of injector seals with an upper and lower O-ring. O- rings and insulators should always be replaced when injectors are removed; they should never be re-used. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 279. Air Assist System To promote better fuel atomization, the 3VZ- FE engine uses an air assist system which meters air from the Idle Speed Control (ISC) valve directly to the nozzle of the fuel injector. An adaptor for the air assist system is added to a standard two-hole type injector to provide an air distribution gallery. Air is mixed with fuel in the chamber formed by the injector insulator grommet and the lower O-ring. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 280. Types Of Injectors In Use Toyota currently uses four different types of fuel injectors depending on engine application. These can be broken down into pintle type and hole type (cone valve and ball valve), high resistance and low resistance. Pintle Type Injector - This was the original design used on early Conventional and EFI/ TCCS engines. This injector gets its name from the type of valve used to control fuel atomization and flow. It offers good atomization of fuel but is susceptible to deposit buildup on the pintle valve. Deposits cause restriction to fuel flow promoting lean fuel delivery and altered injector spray pattern. Hole Type Injector - Hole type injectors were introduced on later model EFI/TCCS engines to reduce concerns with injector deposits. The inject.on valve is recessed from the tip of the injector and fuel is delivered through holes drilled in a director plate at the injector tip. The hole type injector offers good fuel atomization while demonstrating better resistance to deposit buildup compared to the pintle design. There are currently three designs of hole type injectors in use, including a side feed injector used on the 3S- GTE and 2TZ-FE engines. High And Low Resistance Injector Windings There are two different types of injector coil windings used depending on the type of drive circuit used and whether or not an external resistor is being used. Low resistance injectors, which typically range between 2 - 3 Ω @ 70'F, are used with an external resistor in a voltage controlled driver circuit. Low resistance injectors are also used without an external resistor in a current controlled driver circuit. High resistance injectors, which typically run about 13.8 Ω @ 70'F, do not require the use of an external resistor in a voltage controlled driver circuit. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 281. Injector Driver Circuits Current is supplied to the ECU driver circuits (#10 and #20 in example) through the fuel injectors. Current flows either directly from the ignition switch or from the EFI Main Relay. When the ECU driver circuit turns on, current flows to ground through the injector solenoid coil. The magnetic field created causes the injector to open against spring tension. When the ECU driver circuit turns off, the spring closes the injector valve. There are two common types of driver circuits currently in use on Toyota EFI engines; both of these driver circuits work on the voltage control principle. One uses an external solenoid resistor and a low resistance injector, the other using a high resistance injector without the solenoid resistor. In both cases, the high circuit resistance is required to limit current flow through the injector winding. Without this control of the current flow through the injector, the solenoid coil would overheat, causing injector failure. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 282. A third type of driver circuit was used by Toyota on overseas models using the 4A-GE engine with D type EFI. Referred to as a current controlled driver circuit, it has never been used by Toyota on vehicles sold in the U.S.A. but is widely used by other auto manufacturers. This type of driver circuit uses a low resistance injector and limits current flow by controlling the gain of the driver transistor. The advantage to the current controlled driver circuit is the short time period from when the driver transistor goes on to when the injector actually opens. This is a function of the speed with which current flow reaches its peak. In terms of injection opening time, the external resistor voltage controlled circuit is somewhat faster than the voltage controlled high resistance injector circuit. The trend, however, seems to be moving toward use of this latter type of circuit due to its lower cost and reliability. The ECU can compensate for slower opening time by increasing injector pulse width accordingly. Caution: Never apply battery voltage directly across a low resistance injector. This will cause injector damage from solenoid coil overheating. Use the proper SST inspection wire will ensure proper series resistance. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 283. Fuel Injection Pattern and Injection Timing Fuel injectors can be pulsed in one of four patterns depending on application. These injection patterns are: • Simultaneous • Two groups of two injectors each (four cylinder engines) • Three groups of two injectors each (six cylinder engines) • Independent (sequential) The following chart represents fuel injection grouping and timing patterns. Because injection timing is based on engine rpm, the ECU must receive an rpm signal to operate the injector driver circuits. With Conventional EFI, this signal comes directly from the coil and is identified as IG. With TCCS, the rpm and crankshaft position identification signals come from the Ne and G1 sensors located in the distributor. If these signals are lost, the ECU will not pulse the injectors. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 284. Fuel Injection Volume Fuel injection volume determination is based upon the value of input sensor signals. In addition to volume control, the ECU can pulse the injectors either synchronously or non-synchronously with ignition events. Both of these topics will be addressed in Chapter 5, "The Electronic Control System." Common Service Concerns and Solutions Injector Maintenance and Cleaning Although it is not the problem it was back in the early to mid '80s, fuel injector restriction is still an issue which needs to be addressed from both a preventative maintenance and repair viewpoint. The best method of injector maintenance is continuous use of high quality fuels with a level of detergency adequate to keep the injector nozzles clean. It is also prudent to offer injector cleaning service using the Toyota approved injector cleaning system and solvents. This service can be offered whenever the vehicle is in for major service to maintain good engine performance and reduce the possibility of expensive injector replacement due to nozzle build-up. It has been established that engines using hole type injectors tend to have fewer problems with fouling than those with pintle type injectors. It has also been established that use of low quality fuels which lack adequate detergent additives can lead to injectors which become flow restrictive or which develop poor spray patterns. When an injector becomes flow restricted, the volume of fuel delivered for a given injection duration will be reduced. This condition will cause lean driveability problems like stumble, hesitation, backfire and surging, especially during open loop operation. When an injector develops a poor spray pattern, fuel is not atomized and vaporized properly. It is entirely possible that the correct volume of fuel will be delivered to the intake manifold, however, this fuel will enter the cylinder as liquid droplets and will not burn. This condition will cause increased hydrocarbon emissions and lean driveability problems just as if the fuel delivery were lean. The symptoms of poor spray pattern can be very similar to those of flow restricted injectors. When it comes time to diagnose these two problems, the recommended procedure is to remove the injectors from the engine and bench flow test each injector using the following tools. This procedure is covered in detail in the appropriate repair manuals. The following information covers the general test procedure. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 285. Caution: Do not create sparks near fuel Injector and graduated cylinder. Keep fire extinguisher nearby while performing this test. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 286. Fuel Starvation Under Load When troubleshooting performance problems which are related to insufficient fuel delivery, the fuel pickup filter should not be overlooked as one possible source of restriction. Contaminants in fuels can restrict this in tank filter sufficiently to cause engine performance problems. In many cases, the engine will perform normally under light load conditions. The in-line filter, although considered to be a "lifetime" filter, can also cause fuel starvation under load and hard starting if it becomes restricted. The best method of diagnosing suspected fuel starvation which takes place under load conditions is road testing with a fuel pressure monitor safely installed on the vehicle. Injector Installation Cautions It is very important to use new O-rings and grommets when installing injectors to prevent leakage of fuel and potential air leaks into the manifold. O-rings should be lubricated with gasoline during installation and injectors should be checked for smooth rotation once installed to ensure proper seating. Finally, many applications use a bi- directional spray pattern which requires precise positioning of the injector in relation to the cylinder head. Use care to follow proper procedures outlined in the appropriate repair manual. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 18 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 287. Injector Placement Placement of injectors by cylinder is not usually necessary; however, starting with the 1991 Tercel 3E-E engine, injectors with two different hole placements are used. The injectors from cylinders number 1 and 3 are not interchangeable with those installed in cylinders number 2 and 4. Always refer to the appropriate repair manual before installing the injectors on the 3E-E or any other engine as this will ensure correct installation. Failure to properly install and position injectors can cause subtle driveability problems which may be difficult to find after the fact. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 19 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 288. Cold Start Injection System To improve engine starting when coolant temperatures are low, a supplementary injector is installed on many EFI engines. The cold start injection system consists of the following components: 1) Cold Start Injector 2) Start Injector Time Switch 3) ECU (most EFI/TCCS) Cold Start Injector The cold start injector is located at some central location in the intake manifold. It is designed to supplement the cranking air/fuel ratio and prime the intake manifold in much the same way as a choke valve does while cranking a carbureted engine. This injector, controlled by the start injector time switch and ECU, sprays a finely atomized mist of fuel while the engine is cranked to improve the speed with which the engine starts. To prevent engine flooding, the injection time is limited by calibration of the start injector time switch and a timer in the ECU. Start Injector Time Switch The function of the start injector time switch is to control the cold start injector ground circuit and to determine maximum injection duration while cranking. Its bi-metallic switch is heated by both engine coolant and an electrical heater. When the engine is cranked, current flows from the STA circuit of the ignition switch to the cold start injector. Current also flows to the heater coils of the start injector time switch. When the bi-metallic contact of the start injector time switch is closed, current flows through the STJ circuit to ground, causing the cold start injector to deliver fuel. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 20 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 289. As the bi-metallic switch is heated by electric current, it opens, causing the STJ circuit to be broken. This prevents the cold start injector from delivering fuel. Heater coils 1 and 2 are wired to accommodate heater current flow whether or not the time switch is closed. When the time switch contact is open, current can still flow through Heat Coil 2, thereby preventing the contact from closing in the middle of a cranking cycle. ECU Cold Start Injector Control On most TCCS engines, an alternate ground may be supplied to the cold start injector by the ECU at the STJ terminal. Based on signals from the coolant temperature sensor, the ECU can operate the cold start The start injector time switch comes in several calibration values. These values determine the maximum temperature and maximum time that the switch will remain closed while the engine is being cranked. Specifications for switch calibration are stamped on the switch. Application information is available through parts and technical service bulletins. injector for up to three seconds regardless of the status of the time switch. Maximum coolant temperature for ECU control is 113’F (45’C), above which the cold start injector will not operate from any source. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 21 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 290. Alternative Method of Cold Cranking Enrichment Some engines have eliminated use of a cold start injector entirely. Starting with the '91 model year, cold start injectors have been eliminated on the 3E-E and 4A-FE engine. During cranking, the ECU looks at THW and lengthens injector pulse width sufficiently to start the engine. Summary In this chapter you have learned that the fuel delivery system pumps fuel from the tank to the engine where it is delivered by an electronically controlled fuel injector. The fuel pump delivers fuel with enough pressure and volume so the fuel pressure regulator can hold a constant pressure differential between intake manifold and fuel rail. Fuel which is delivered to the fuel rail but not injected into the cylinders is returned to the tank through a return pipe. The fuel pump is energized by the circuit opening relay electrical circuit whenever the ignition switch is on and the engine is running or cranking. Depending on fuel demand, some pumps are operated at two speeds by routing current flow through or around a special current limiting resistor. The fuel pump electrical circuit has a diagnostic monitor built into the underhood check connector for diagnosis and testing. Fuel injectors are electrically controlled by the ECU and are driven individually, in groups, or simultaneously, depending on engine application. Current flow through the injector coil is controlled by using a high resistance coil or a separate injector solenoid resistor. To improve cold starting, some engines are equipped with a cold start injector system which is controlled by a start time switch and/or the ECU. Reprinted with permission from Toyota Motor Sale, U.S.A., Inc. from #850 EFI Course Book. EFI #3 - FUEL DELIVERY & INJECTION CONTROL Page 22 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 291. The EFI/TCCS Ignition System Overview of Toyota EFI/TCCS Ignition Control The ignition systems used on today's EFI/TCCS equipped engines are not that much different from the ignition system used on the original 4M-E EFI engine. Primary circuit current flow is controlled by an igniter based on signals generated by a magnetic pickup (pickup coil) located in the distributor. The ignition system has a dual purpose, to distribute a high voltage spark to the correct cylinder and to deliver it at the correct time. Ideal ignition timing will result in maximum combustion pressure at about 10' ATDC. The most significant difference between TCCS and Conventional EFI ignition systems is the way spark advance angle is managed. The Conventional EFI system uses mechanical advance weights and vacuum diaphragms to accomplish this. Starting with the 5M-GE engine in 1983, the TCCS system controls ignition spark timing electronically and adds an ignition confirmation signal as a fail-safe measure. There are two versions of electronic spark management used on TCCS equipped engines, the Electronic Spark Advance (ESA) and the Variable Advance Spark Timing (VAST) systems. EFI #4 - TCCS IGNITION SYSTEM Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 292. Conventional EFI Ignition System Spark Advance Angle Control In the Conventional EFI system, spark advance angle is determined by the position of the distributor (initial timing), position of the magnetic pickup reluctor teeth (centrifugal advance), and position of the breaker plate and pickup coil winding (vacuum advance). The spark advance curve is determined by the calibration of the centrifugal and vacuum advance springs. Besides being subject to mechanical wear and mis-calibration, this type of spark advance calibration is very limited and inflexible when variations in coolant temperature and engine detonation characteristics are considered. Mechanical control of a spark curve is, at best, a compromise. In some cases the timing is optimal; in most cases it is not. Engine RPM Signal To indicate engine rpm to the EFI computer, the Conventional EFI system uses the signal generated at the coil negative terminal (IG-). Because this system does not use ECU controlled timing, the rpm signal to the ECU has no impact on spark timing whatsoever. The IG signal is used as an input for fuel injection only. EFI #4 - TCCS IGNITION SYSTEM Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 293. Conventional EFI Ignition System Operation When the engine is cranked, an alternating current signal is generated by the pickup coil. This signal is shaped in the igniter and then relayed through a control circuit to the base of the primary circuit power transistor. When the voltage at the base of this transistor goes high, current begins to flow through the coil primary windings. When this signal goes low, coil primary current stops flowing, and a high voltage is induced into the secondary winding. At cranking speed, spark plugs fire at initial timing, a function of distributor position in the engine. When the engine is running, spark timing is determined by the relative positions of the pickup reluctor (signal rotor) and the pickup coil winding to each other. This relative position is controlled by the centrifugal advance weights and vacuum advance diaphragm positions. As engine speed increases, the reluctor advances in the same direction as distributor shaft rotation. This is a result of the centrifugal advance operation. As manifold vacuum applied to the vacuum controller is increased, the pickup coil winding is moved opposite to distributor shaft rotation. Both of these conditions cause the signal from the pick-up coil to occur sooner, advancing timing. EFI #4 - TCCS IGNITION SYSTEM Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 294. TCCS Ignition Spark Management, Electronic Spark Advance (ESA), and Variable Advance Spark Timing (VAST) The advent of ECU spark management systems provides more precise control of ignition spark timing. The centrifugal and vacuum advances are eliminated; in their place are the engine sensors which monitor engine load (Vs or PIM) and speed (Ne). Additionally, coolant temperature, detonation, and throttle position are monitored to provide better spark accuracy as these conditions change. To provide for optimum spark advance under a wide variety of engine operating conditions, a spark advance map is developed and stored in a look up table in the ECU. This map provides for accurate spark timing during any combination of engine speed, load, coolant temperature, and throttle position while using feedback from a knock sensor to adjust for variations in fuel octane. TCCS engines use two versions of ECU controlled spark management, Electronic Spark Advance (ESA) and Variable Spark Timing (VAST). EFI #4 - TCCS IGNITION SYSTEM Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 295. To monitor engine rpm, the TCCS system uses the signal from a magnetic pickup called the Ne pickup. The Ne pickup is very similar to the magnetic pickup coil used with Conventional EFI. It has either four or 24 reluctor teeth, depending on engine application. Engines equipped with the ESA system (and the 4A-GE engine with VAST) use a second pickup in the distributor called the G sensor. The G sensor supplies the ECU with crankshaft position information which is used as a reference for ignition and fuel injector timing. Some engines use two G sensors, identified as G1 and G2. ESA Ignition System Operation In the example above, when the engine is cranked, an alternating current signal is generated by a 24-tooth Ne pickup and a four-tooth G pickup. These signals are sent to the ECU where they are conditioned and relayed to the microprocessor. The microprocessor drives a trigger circuit, referred to as IGt (TR1). The IGt signal is sent to the igniter to switch the primary circuit power transistor on and off. While cranking, IGt fixes spark timing at a predetermined value. When the engine is running, timing is calculated based on signals from engine speed, load, temperature, throttle position, and detonation sensors. The IGt signal is advanced or retarded depending on the final calculated timing. ESA calculated timing is considered the ideal ignition time for a given set of engine conditions. If the ECU fails to see an Ne or G signal while it is cranking, it will not produce an IGt signal, thus preventing igniter operation. EFI #4 - TCCS IGNITION SYSTEM Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 296. VAST System Operation When the engine is cranked, an alternating current signal is generated by a four-tooth magnetic pickup in the distributor. This alternating current signal is sent directly to the igniter where it is conditioned into a square wave by a waveform shaping circuit. While cranking, this square wave signal is sent to the ECU on the Ne wire and to the igniter power transistor. The ignition system delivers spark at initial timing under this condition. When the engine starts and exceeds a predetermined rpm, the ECU begins sending the lGt signal to the igniter. The igniter switches to computed timing mode and uses the IGt signal to operate the power transistor. Timing of IGt is based on information from various engine sensors. Because the VAST system triggers the igniter directly from the magnetic pickup while cranking, the engine will start even if the IGt circuit to the igniter is open. If IGt signals are not received by the igniter once the engine has started, it will continue to run, defaulted at initial timing, using signals from the magnetic pickup. The VAST system is only used on the 2S-E, 22R-E, 22R-TE, 4Y-E, and 4A-GE engines. EFI #4 - TCCS IGNITION SYSTEM Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 297. Igniter Operation When the IGt signal goes high, the primary circuit power transistor TR2 turns on, allowing cur-rent to flow in the coil primary winding. When the IGt signal goes low, the igniter interrupts primary circuit current flow, causing voltage induction into the coil secondary winding. With the ESA system, the time at which the power transistor in the igniter turns on is further influenced by a dwell control circuit inside the igniter. As engine rpm increases, coil dwell time is increased by turning the transistor on sooner. Therefore, the time at which the transistor is turned on determines dwell while the time the transistor is turned off determines timing. Timing is controlled by the ECU; dwell is controlled by the igniter. Controlling dwell within the igniter allows the same control over coil saturation time as the ballast resistance does with the Conventional EFI ignition system. It allows maximum coil saturation at high engine speeds while limiting coil and igniter current, reducing heat, at lower speeds. Spark Confirmation IGf Once a spark event takes place, an ignition confirmation signal called IGf is generated by the igniter and sent to the ECU. The IGf signal tells the ECU that a spark event has actually occurred. In the event of an ignition fault, after approximately eight to eleven IGt signals are sent to the igniter without receiving an IGf confirmation, the ECU will enter a fail-safe mode, shutting down the injectors to prevent potential catalyst overheating. EFI #4 - TCCS IGNITION SYSTEM Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 298. ECU Detection Of Crankshaft Angle ESA System In order to correctly time spark and injection events, the ECU monitors the relationship between the Ne and G signals. With most engines, the ECU determines the crankshaft VAST System Because all engines which use this system have a simultaneous injection pattern (except the 4A-GE), a G signal is not necessary. The four-toothed pickup is designed to produce a pulse once every 180' of crankshaft rotation, signal timing determined by the position of the distributor in the engine. Distributor position determines Ne signal timing and, therefore, initial timing reference. The 4A-GE engine with VAST, because it uses grouped injection, utilizes a G sensor signal indicating camshaft position so the ECU can properly time each injector group. has reached 10' BTDC of the compression stroke when it receives the first Ne signal following a G1 (or G2). Initial timing adjustment is critical as all ECU timing calculations assume this initial 10' BTDC as a reference point for the entire spark advance curve. Ignition Timing Strategy The ECU determines ignition timing by comparing engine operating parameters with spark advance values stored in its memory. The general formula for ignition timing follows: Initial timing + Basic advance angle + Corrective advance angle = Total spark advance. Basic advance angle is computed using signals from crankshaft angle (G1), crankshaft speed (Ne), and engine load (Vs or PIM) sensors. Corrective timing factors include adjustments for coolant temperature (THW) and presence of detonation (KNK). EFI #4 - TCCS IGNITION SYSTEM Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 299. Distributor-Less Ignition System (DLI) Used only on the 7M-GTE engine, DLI, as the name implies, is an electronic spark distribution system which supplies secondary current directly from the ignition coils to the spark plugs without the use of a conventional distributor. The DLI system contains the following major components: 1) Cam Position Sensor 2) Igniter 3) Ignition Coils (3) Cam Position Sensor Very similar to the 7M-GE distributor without the secondary distribution system, the cam position sensor houses the Ne, G1, and G2 pickups. The Ne pickup reluctor has 24 teeth, its signal representing crankshaft speed. The G1 and G2 pickups produce signals near TDC compression stroke for cylinders #6 and #1, respectively. These signals represent standard crankshaft angle and cylinder identification. Igniter The igniter is similar to those used on distributor type ignition systems but incorporates three separate primary circuits. The igniter determines timing of three primary circuits by the combination of IGdA and IGdB input signals from the ECU. The IGt signal is relayed by the igniter to the proper power transistor circuit to trigger the ignition event at the proper coil. The igniter also sends the standard IGf confirmation signal to the ECU for each ignition event which takes place. EFI #4 - TCCS IGNITION SYSTEM Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 300. Ignition Coils Each coil is connected in series between spark plugs of companion cylinders. For every engine cycle (720' of crankshaft rotation), ignition is carried out twice at each coil, both spark plugs firing simultaneously. One plug fires before TDC on the compression stroke while the companion fires at the same position before TDC on the exhaust stroke. This type of secondary distribution is referred to as waste spark. The three ignition coils are mounted on the top of the engine to the upper section of the head cover. As you face the engine, the coil for the 1-6 cylinder pair is on your left. The coil in the center serves the 3-4 cylinder pair, and the coil to the right serves cylinder pair 2-5. EFI #4 - TCCS IGNITION SYSTEM Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 301. DLI System Operation When the engine is cranked, alternating current signals are generated by the 24-tooth Ne sensor and the two G sensors (G1 and G2). The G sensors are 360' out of phase. The G sensors represent #1 and #6 pistons approaching TDC on the compression stroke. These signals are received by the ECU where they are conditioned and processed by the ESA microprocessor. The ESA microprocessor serves two functions. It generates an IGt signal and generates cylinder identification signals, IGdA and IGdB, which allow the DLI igniter to trigger the correct coil while cranking the engine. These signals are sent to the DLI igniter which electronically determines proper primary signal distribution based on the combination of IGdA and IGdB signals. The igniter distributes the IGt signal to the proper coil driver circuit and determines dwell period based on coil primary current flow. The ESA calculations for spark advance angle work the same as with distributor type ignition systems. The table below shows how the igniter is able to calculate crankshaft position and properly distribute the IGt signal to the transistor driver circuit connected to the relevant ignition coil. EFI #4 - TCCS IGNITION SYSTEM Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 302. Ignition System Service Troubleshooting the Ignition System No Spark Output The following procedures assume that a spark tester reveals no spark at two different cylinders while the engine is cranked. These procedures and specifications are general guidelines. Consult the appropriate repair manual for more specific information about the vehicle you are troubleshooting. Preliminary checks 1) Ensure battery condition prior to ignition system analysis. 2) Check and confirm good connections at distributor, igniter, and coil. 3) Basic secondary leakage checks at coil and coil wire. Primary circuit checks 1) Confirm power supply to igniter and coil positive (+) terminal. Confirm connections at coil positive and negative (-) terminals. 2) Using a test light or logic probe, check for primary switching at the coil (-) terminal while cranking engine. Blinking light confirms primary switching is taking place; check coil wire, coil secondary winding resistance, or secondary leakage in distributor cap. 3) The power transistor(s) in the igniter get their ground through the igniter case to the vehicle chassis; always confirm good ground continuity prior to trouble shooting. 4) Confirm coil primary and secondary windings resistance. Confirm primary windings are not grounded. 5) Confirm signal status from Ne and G pickups to ECU (ESA system) or to igniter (VAST system) using an oscilloscope or logic probe. • If a fault is detected, check pickup(s) for proper resistance and shorts to ground. Check electrical connections. • If signal amplitude is low, check signal generator gap(s). 6) Confirm signal status from ECU IGt circuit to igniter using an oscilloscope or logic probe. 7) On 7M-GTE, check power transistor in igniter. Bias transistor base using a remote 3 volt battery as power source. Use ohmmeter to check for continuity from primary circuit to ground (see procedure in repair manual for details). EFI #4 - TCCS IGNITION SYSTEM Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 303. 8) Check pickup gaps and coil resistances against specifications. If gap and/or resistance is not within specification, replace faulty component. EFI #4 - TCCS IGNITION SYSTEM Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 304. Timing Will Not Advance Properly (VAST System) The following checks assume that the engine runs but timing will not advance. The design of the VAST system will allow the ignition system to function at initial timing in the event that the IGt signal does not reach the igniter. If this condition occurs, the ignition system will be locked at initial timing regardless of engine speed or load. The ECU has no way to monitor for this fault, so there will be no indication of this condition other than a loss of engine performance. To check for this condition: 1) Monitor the IGt wire at the igniter using an oscilloscope or logic probe. 2) If a good signal is being sent out on IGt, check the connection at the igniter. 3) Once connections are confirmed, the igniter is the last item left which can cause the problem. Timing Seems Out of Range For Conditions (VAST or ESA) In some cases, driveability symptoms or a check of timing reveal advance which is out of range for input conditions. This situation could be caused by incorrect sensor information reaching the ECU. An example of this type of problem can be illustrated by a manifold pressure sensor which is out of range low. Lower than normal voltage from the sensor would indicate a light load condition to the ECU. The ECU responds to light load operation by advancing the timing. If the vehicle is being operated under moderate to heavy load with too much spark advance, detonation will likely result. When this type of condition is suspected, it is recommended to perform a standard voltage check of all major sensor inputs to the ECU. If any sensor is found out of normal range, it is a likely cause of the problem. The subject of sensor signal values is addressed in, "Electronic Engine Controls." EFI #4 - TCCS IGNITION SYSTEM Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 305. Adjustment Of Initial Ignition Timing All engines equipped with TCCS utilize a test terminal (T or TE1) somewhere under the hood. Early TCCS utilizes a two-terminal check connector in the wiring harness. This yellow body connector contains circuits T and E1, which when jumpered, default the TCCS system to initial timing. The location of this test terminal varies between applications. Refer to the appropriate repair manual for connector location. A new design multipurpose check connector began phase-in starting with 1985 models. By 1986 model year, all vehicles are equipped with this new style connector. Connectors are typically located in the fender area on either side, or near the bulkhead, in plain view. With the advent of test terminals for the ECT, TEMS, SRS, and etc., the TCCS test terminal has been renamed TE1 to distinguish it from the others. To check timing on any TCCS equipped engine: 1) Engine at normal operating temperature. 2) Jumper T (TE1) to El using SST 09843-18020 (or equivalent). 3) Wait for engine rpm to stabilize (speed may rise to I K to 1.3 K rpm for 5 seconds). 4) Use timing light to confirm initial timing as per repair manual procedure. • Make sure rpm is within specified range. • Adjust timing as necessary by rotating the distributor (cam position sensor on 7M-GTE). 5) Remove SST jumper. 6) Recheck timing; it should be advanced (at least 3' to 18') from initial with SST removed. EFI #4 - TCCS IGNITION SYSTEM Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 306. Summary In this chapter you have learned how the ECU electronically controls ignition timing, delivering spark at the optimum moment based on engine speed, load, temperature and quality of fuel. The spark advance curve is stored in a look up table in the ECU memory. There are two types of ECU controlled spark advance systems used on Toyota TCCS equipped engines, the Variable Advance Spark Timing system (VAST) and the Electronic Spark Advance system (ESA). The main difference between these systems is the magnetic pickup in the distributor (Ne pickup) reports to the igniter on the VAST system and directly to the ECU on the ESA system. An ignition confirmation signal is generated by the igniter which signals the ECU with each ignition event. The IGf signal is used to provide the ECU with a fail-safe fuel cutoff if ignition spark is lost. The Distributorless Ignition system (DLI) provides secondary distribution by means of a three-coil waste spark system. Two companion spark plugs are connected to each end of the ignition coil secondary windings. These plugs fire simultaneously each time the cylinder pair approaches TDC, one spark igniting the mixture, the other wasted on the exhaust stroke. Reprinted with permission from Toyota Motor Sale, U.S.A., Inc. from #850 EFI Course Book. EFI #4 - TCCS IGNITION SYSTEM Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 307. Overview The EFl/TCCS system is an electronic control system which provides Toyota engines with the means to properly meter the fuel and control spark advance angle. The system can be divided into three distinct elements with three operational phases. The three system elements are: • Input Sensors • Electronic Control Unit (A Microcomputer) • Output Actuators ENGINE CONTROLS - INPUT SENSORS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 308. The electronic control system is responsible for monitoring and managing engine functions which were previously performed by mechanical devices like carburetors, vacuum, and centrifugal advance units. In an electronic control system, these functions are managed in three phases. • The input phase of electronic control allow the Electronic Control Unit (ECU) to monitor engine operating conditions, utilizing information from the input sensors. • The process phase of electronic control requires the ECU to use this input information to make operating decisions about the fuel and spark advance systems. • The output phase of electronic control requires the ECU to control the output actuators, the fuel injectors, and igniter to achieve the desired fuel metering and spark timing. In this chapter, we will explore the details of the electronic control system hardware and software. The chapter starts with a thorough examination of the system's input sensor circuits and the ECU power distribution system. It concludes with a closer look at the ECU process functions and the control strategy use( for optimum fuel metering and spark advance angle control. The Microcomputer The heart of the TCCS system is a microcomputer. A microcomputer is a device which receives information, processes it, and makes decisions based on a set of program instructions. The microcomputer exercises control over the output actuators to carry out these instructions. The use of microcomputers has taken the science of engine management into the space age by increasing the speed with which information can be processed and allowing the electronic control system to manage more engine functions. With the ability to process information so rapidly, the modern ECU is capable of carrying out its programmed instructions with extreme accuracy. Engine management can address virtually every condition the engine will encounter so that for any engine condition, the ECU will deliver optimum fuel and spark. Evolution of Toyota's Electronic Fuel Injection Systems Early Conventional EFI computers were first configured from analog circuits, and they controlled only fuel delivery and injection. The modem Electronic Control Units (ECU) utilize digital circuits and microprocessors which have served to improve EFI system capabilities. Modern TCCS engine controls, introduced to the U.S.A. market in 1983, are capable of managing fuel delivery, idle speed control (ISC), electronic spark advance (ESA), and emissions systems with extraordinary speed and accuracy. In the evolution of Toyota's fuel injection, three levels of electronic control refinements have taken place. • Conventional EFI • P7/EFI • EFI/TCCS The main difference between these systems is the capability of the ECU. These capabilities have grown from simple fuel control to the addition of self-diagnostics to the control of ignition spark advance and more. The following chart summarizes basic capabilities by system and can be used as a guide in identification and troubleshooting. ENGINE CONTROLS - INPUT SENSORS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 309. System identification is relatively simple. • The Conventional EFI system has no check engine light. • The P7/EFI system has a check engine light but has a mechanical advance distributor. • The EFI/TCCS system has a check engine light and an electronic advance distributor. The Input Sensors, Information Source for the ECU In an electronic control system, the ECU uses its sensors in much the same manner as we use our five senses. Our sense of touch tells us when things are hot or cold; our sense of hearing allows us to distinguish one sound from another; our sense of smell tells us when fresh coffee is brewing somewhere nearby. Sensors give the ECU similar abilities: the ability to feel the temperature of the engine coolant, to listen for the sound of detonation, and to smell the exhaust stream for the presence of sufficient oxygen. This lesson on input sensors will address how each major ECU input sensor circuit works. Each sensor circuit will be broken down so you can see its individual components: the sensor, electrical wiring, and the ECU. ENGINE CONTROLS - INPUT SENSORS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 310. Overview The EFl/TCCS system is an electronic control system which provides Toyota engines with the means to properly meter the fuel and control spark advance angle. The system can be divided into three distinct elements with three operational phases. The three system elements are: • Input Sensors • Electronic Control Unit (A Microcomputer) • Output Actuators ENGINE CONTROLS - INPUT SENSORS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 311. Input Sensors Used in Basic Injection and Spark Calculation Engine Air Flow Sensing Vane Type Air Flow Meters (Vs, General Information) The vane type air flow meter is located in the air induction system inlet pipe between the air cleaner and the throttle body. It is composed of the measuring plate, compensation plate, return spring, potentiometer, and by-pass passage. The sensor also incorporates the idle mixture adjusting screw (factory sealed), the fuel pump switch, and the intake air temperature sensor (which will be addressed later in this lesson). Because intake air volume is a direct measure of the load placed on an engine, the vane type air flow meter provides the most important input to the ECU for fuel and spark calculations. When air passes through the air flow meter, it forces the measuring plate open to a point where it balances with the force of the return spring. The damping chamber and compensation plate prevent vibration of the measuring plate during periods of sudden intake air volume changes. The potentiometer, which is connected to the measuring plate and rotates on the same axis, converts the mechanical movement of the measuring plate into a variable voltage signal. Movement of the measuring plate and the analog voltage signal produced by this sensor are proportional to the volume of air entering the intake manifold. Vane Air How Meter Electrical Circuit The sensor movable contact is attached to the measuring plate and rides on a fixed resistor wired between the reference voltage input and the ground. As the volume of air entering the engine increases, the movable contact moves across the fixed resistor, causing a change in signal output voltage. There are two designs of vane air flow meters used on Toyota L type EFI systems. The first design generates a signal which varies from low voltage at low air volumes to high voltage at high air volumes. The second design sensor has opposite signal characteristics. These sensors also operate on different reference voltages. Both sensor designs integrate an intake air temperature sensor into the air flow meter. ENGINE CONTROLS - INPUT SENSORS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 312. First Design Vane Air How Meter The first design air flow meter is found on all Conventional EFI engines and many later model TCCS equipped engines. This sensor has an electrical connector with seven terminals, four of which are used for air flow measurement. Air Flow Sensor Terminal Identification (First Design Sensor) The air flow meter and ECU are wired as shown in the diagram. Signal characteristics are depicted by the accompanying graph. The use of battery voltage, VB, as a sensor input necessitates the use of the Vc terminal as a constant reference signal for the ECU. This is because battery voltage may change with variances in electrical load and ambient temperatures. Without the use of a constant reference voltage, these changes would cause a change in the Vs signal value recognized by the ECU. ENGINE CONTROLS - INPUT SENSORS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 313. Second Design Air How Meter The second design air flow meter was introduced on the '85 5M-GE engine, and its use expanded with many late model TCCS equipped engines. This sensor has an electrical connector with seven terminals, three of which are used for air flow measurement. Air Flow Sensor Terminal Identification (Second Design Sensor) The air flow meter and ECU are wired as shown in the diagram; signal characteristics are depicted by the accompanying graph. The use of a regulated 5 volt reference eliminates the need for the VB terminal with this sensor circuit. Resistors R1 and R2 provide self diagnostic capabilities and allow for a fail-safe voltage at the ECU in the event of an open circuit. These two resistors have a very high resistance value (relative to r1 and r2) and essentially have no electrical effect on the circuit under normal operating conditions. They will, however, affect the open circuit voltage measured on the Vs wire at the ECU. ENGINE CONTROLS - INPUT SENSORS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 314. Karman Vortex Air Flow Meter (Ks) The Karman vortex air flow meter is currently used on the 7M-GTE Toyota engine and the 2JZ-GE and 1UZ-FE Lexus engines. It is located in the air induction system inlet pipe between the air cleaner and the throttle body. The sensor is composed of a photocoupler and mirror, a vortex generator, and an integrated circuit (IC) which together, measure the frequency of the vortices generated by air entering the intake system. When compared with the vane type air flow meter, the Karman vortex meter is smaller, lighter, and offers less restriction to incoming air. Similar to the vane type air meter, the Karman vortex meter integrates the intake air temperature sensor into the meter assembly. The sensor has an electrical connector with five terminals, three of which are used for air flow measurement. Karman Vortex Air Flow Meter Terminal Identification ENGINE CONTROLS - INPUT SENSORS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 315. The Karman vortex air flow meter and ECU are wired as shown in the diagram. Signal characteristics are represented by the illustration of the variable frequency square wave. Because of the pull-up resistor wired between the Vcc and Ks circuit, the Ks signal will go to 5 volts if the circuit is opened. When air passes through the air flow meter, the vortex generator creates a swirling of the air downstream. This swirling effect is referred to as a "Karman vortex." The frequency of this Karman vortex varies with the velocity of the air entering the air flow meter and other variables. The photocoupler and metal foil mirror are used to detect changes in these vortices. ENGINE CONTROLS - INPUT SENSORS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 316. The metal foil mirror is used to reflect light from the LED to the photo transistor. The foil is positioned directly above a pressure directing hole which causes it to oscillate with the changes in vortex frequency. As the mirror oscillates, the 5 volt Vcc reference is switched to ground by a photo transistor within the sensor. The resulting digital signal is a 5 volt square wave which increases in frequency in proportion to increases in intake air flow. ENGINE CONTROLS - INPUT SENSORS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 317. Manifold Absolute Pressure Sensor The manifold absolute pressure sensor (sometimes referred to as vacuum sensor) is used on engines equipped with D type EFI. It is typically located somewhere on the bulkhead with a vacuum line leading directly to the intake manifold. It measures intake air volume by monitoring changes in manifold absolute pressure, a function of engine load. The sensor consists of a piezoresistive silicon chip and an Integrated Circuit (IC). A perfect vacuum is applied to one side of the silicon chip and manifold pressure applied to the other side. When pressure in the intake manifold changes, the silicon chip flexes, causing a change in its resistance. The varying resistance of the sensor causes a change in signal voltage at the PIM (Pressure Intake Manifold) terminal. ENGINE CONTROLS - INPUT SENSORS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 318. The manifold absolute pressure sensor has an electrical connector with three terminals. Manifold Absolute Pressure Sensor Terminal Identification The sensor and ECU are wired as shown in the diagram. As manifold pressure increases (approaches atmospheric pressure) there is a proportionate increase in PIM signal voltage. This analog signal characteristic is depicted in the accompanying graph. TO check sensor calibration, signal voltage should be checked against the standards shown on the graph, and a voltage drop check should be performed over the entire operating range of the sensor. ENGINE CONTROLS - INPUT SENSORS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 319. Engine Speed and Crankshaft Angle Sensing On TCCS equipped engines, the Ne and G1 signals inform the ECU of engine rpm and crankshaft angle. This information, along with information from the air flow or manifold pressure sensor, allows the ECU to calculate the engine's basic operating load. Based on measured load, basic injection and spark advance angle can be accurately calculated. Ne Signal (Number of Engine Revolutions) The Ne signal generator consists of a pickup coil and toothed timing rotor. The number of teeth on the signal timing rotor is determined by the system used. The Ne sensor produces an alternating current waveform signal and is of critical importance to the ECU. If this signal fails to reach the ECU, the engine will not run. G or G1 Signal (Group #1) The G signal generator is very similar to the Ne signal generator. The G1 signal represents the standard crankshaft angle and is used by the ECU to determine ignition and injection timing in relation to TDC. Depending on engine, there are different variations of Ne and G1 signal generators. The following illustrations show the relationship between the Ne and G1 signals and the different variations of signal generators. ENGINE CONTROLS - INPUT SENSORS Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 320. ENGINE CONTROLS - INPUT SENSORS Page 14 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 321. lGf Signal The IGf signal is generated by the igniter on EFI/TCCS systems. The ECU supplies a 5 volt reference through a pull-up resistor to the lGf signal generation circuit in the igniter. When a spark plug fires, the IGf signal generation circuit pulls the five volts to ground, causing a pulse to be sensed at the ECU. One pulse is generated by the igniter for each ignition event which is carried out. IG Signal On Conventional EFI engines, the IG signal is used to inform the ECU of engine rpm. This signal is generated directly from the coil negative terminal or from an electrically equivalent point inside the igniter on the early The IGf signal confirms that ignition has actually occurred. In the event of a failure to trigger an ignition event, the ECU will shut down injector pulses to protect the catalyst from flooding with raw fuel. Typically this fail- safe shutdown occurs within eight to eleven IGt signals after the IGf signal is lost. This condition can occur with any primary ignition system fault, an igniter failure, a problem with the IGf circuit wiring, or with a faulty ECU. P-7 2S-E engine. Conventional EFI engines do not use an Ne or G sensor and do not use an IGf signal. The IG signal is also used by the ECU to trigger injection pulses; therefore, if this signal is lost, the engine will stall for lack of injection pulse. ENGINE CONTROLS - INPUT SENSORS Page 15 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 322. Input Sensors Used For Injection and Spark Corrections Water Temperature Sensor (THW) The water temperature sensor is typically located near the cylinder head water outlet. It monitors engine coolant temperature by means of an internally mounted thermistor. The thermistor has a negative temperature coefficient (NTC), so its resistance value decreases as coolant temperature rises. The accompanying resistance graph demonstrates this relationship. The water temperature sensor is required because fuel vaporization is less efficient when the engine is cold. Internal engine friction is also higher during cold operation, increasing operating load. The THW signal is used by the ECU to determine how much fuel enrichment correction is necessary to provide good cold engine performance. In addition to fuel calculations, the THW signal plays a major role is almost every other function that the ECU serves. ENGINE CONTROLS - INPUT SENSORS Page 16 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 323. The water temperature sensor has a two terminal electrical connector attached to either end of the thermistor element. Water Temperature Sensor Terminal Identification The sensor and ECU are wired as shown in the diagram. Signal voltage characteristics are determined by the value of the pull-up resistor, located inside the ECU, either 2.7 KΩ or 5 M. The graphs accompanying the diagram give approximate voltage specifications. To determine which pull-up resistor a particular ECU uses, refer to the technical reference charts in Appendix B of this book. ENGINE CONTROLS - INPUT SENSORS Page 17 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 324. Air Temperature Sensor (THA) The air temperature sensor monitors the temperature of air entering the intake manifold by means of a thermistor. This thermistor is integrated within the air flow meter on L type systems and located in the intake air hose just downstream of the air cleaner on D type systems. It has the same resistance characteristics as the water temperature sensor. ENGINE CONTROLS - INPUT SENSORS Page 18 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 325. This sensor has a two-terminal electrical connector attached to either end of the thermistor element. Air Temperature Sensor Terminal Identification The air temperature sensor and ECU are wired as shown in the diagram. Resistance and voltage signal characteristics are represented by the accompanying graphs. An intake air temperature monitor is necessary in the EFI system because the pressure and density of air changes with temperature. Because air is more dense when cold, the ECU factors intake air temperature into the fuel correction program. ENGINE CONTROLS - INPUT SENSORS Page 19 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 326. Throttle Angle and Closed Throttle Sensing Throttle position sensors typically mount on the throttle body, directly to the end of the throttle shaft. Depending on engine and model year, Toyota EFI equipped engines use one of two different types of throttle position sensors. These sensors are categorized as on-off type and linear type. The linear type sensor is typically used on most late model Electronically Controlled Transmission (ECT) equipped vehicles. The on-off type sensor circuits can be further broken down into first and second design. This sensor is typically used on manual or non-ECT transmission equipped applications. All throttle sensors, regardless of design, supply the ECU with vital information about idle status and driver demand. This information is used by the ECU to make judgments about power enrichment, deceleration fuel cut-off, idle stability, and spark advance angle corrections. ENGINE CONTROLS - INPUT SENSORS Page 20 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 327. On-Off Type Throttle Position Sensors (IDL & PSW) The on-off type throttle position sensor is a simple switch device which, depending on application, either pulls a reference voltage to ground or sends a battery voltage signal to the ECU. The on-off throttle position sensors are electrically wired to the ECU as shown in the accompanying diagrams. First Design On-Off Type Sensor The first design sensor is used on Conventional EFI engines. It utilizes a dual position contact which switches a battery voltage signal to either the IDL or PSW inputs at the ECU. This switching action causes the voltage signal at the ECU to go high whenever the switch contacts are closed. Referring to the voltage graph, IDL signal voltage is high when the throttle is closed and goes low when the throttle exceeds a 1.5' opening. PSW voltage is low until the throttle exceeds about a 70' opening; then it goes high. ENGINE CONTROLS - INPUT SENSORS Page 21 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 328. Second Design On-Off Type Sensor The second design sensor, which is used on many late model TCCS equipped engines, utilizes a dual position contact to switch an ECU reference voltage to ground. This switching action causes the signal at the ECU to go low whenever the switch contacts are closed. Referring to the voltage graph, IDL signal voltage is low when the throttle is closed and goes high when the throttle exceeds a 1.5' opening. PSW voltage is high until the throttle opens to about 70’; then it goes low. The three wire electrical connector terminals are identified as follows. 1 st and 2nd Design On-Off Throttle Position Sensor Terminal Identification ENGINE CONTROLS - INPUT SENSORS Page 22 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 329. On '83 and '84 Cressidas/Supras and '83 through '86 Camrys equipped with an Electronically Controlled Transmission (ECT), a modified sensor, which incorporates three additional signal wires designated L1, L2, and L3, is used. These signals represent throttle opening angles in between the 1.5' IDL and 70' PSW signals. The L1, L2, and L3 signals are used by the ECT system and are generated in a similar manner as the IDL and PSW signals on the 2nd design sensor. The TCCS ECU only uses the IDL and PSW signals from this sensor. Linear Throttle Position Sensor (VTA) The linear throttle position sensor is mounted to the throttle body. It is composed of two movable contacts, a fixed resistor, and four electrical terminals. The two movable contacts move along the same axis as the throttle valve. One is used for the throttle opening angle signal (VTA) and the other for the closed throttle signal (IDL). ENGINE CONTROLS - INPUT SENSORS Page 23 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 330. As the throttle opens, a potentiometer circuit converts the mechanical movement of the throttle valve into a variable voltage signal. The voltage produced by this sensor is proportional to the throttle valve opening angle. The Linear Throttle Position Sensor has an electrical connector with four terminals. Linear Throttle Position Sensor Terminal Identification The sensor and ECU are wired as shown in the diagram. As the throttle valve opens, the sensor VTA contact moves closer to the voltage source, causing a signal voltage increase. At closed throttle, the IDL contact is held closed. This pulls the IDL signal circuit to ground. As the throttle opens, the IDL contact breaks, causing the digital IDL signal voltage to go from low to high. These signal characteristics are depicted in the accompanying graph. Resistors R1 and R2 provide self diagnostic capabilities and allow for a fail-safe voltage at the ECU in the event of an open circuit. These two resistors have a very high resistance value and essentially have no electrical effect on the circuit under normal operating conditions. They will, however, affect the open circuit voltage measured on the VTA wire at the ECU. ENGINE CONTROLS - INPUT SENSORS Page 24 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  • 331. Exhaust Oxygen Content Sensing (OX1) Exhaust oxygen sensors are used on Toyota EFI and EFI/TCCS equipped engines to provide air/fuel ratio feedback information to the ECU. This information is used to constantly adjust the air/fuel ratio to stoichiometry during warm idle and cruise operating conditions. The stoichiometric air/fuel ratio delivers one pound of fuel for each 14.7 pounds of air entering the intake manifold and results in the most efficient combustion and catalyst operation. When the electronic control system is using information from the oxygen sensor to adjust air/fuel ratio, the system is said to be operating in closed loop. Exhaust oxygen sensor efficiency is dependent upon its operating temperature. The sensor will only generate an accurate signal when it has reached its minimum operating temperature of 750'F. Therefore, the oxygen sensor is typically located in the exhaust stream at the manifold collector. This location is close enough to the exhaust valves to maintain adequate operating temperature under most driving conditions and allows a representative exhaust sample from all cylinders. Open and Closed Loop Operation In addition to promoting efficient combustion and catalyst operation, a stoichiometric air/fuel ratio also promotes excellent fuel economy. This relatively lean mixture is desirable during cruise and idle operation; however, other operating conditions often require a richer air/fuel ratio. When the electronic control system ignores signals from the oxygen sensor and does not correct the air/fuel ratio to 14.7:1, the system is said to be operating in open loop. In order to prevent overheating of the catalyst and ensure good driveability, open loop operation is required under the following conditions: • During engine starting • During cold engine operation • During moderate to heavy load operation • During acceleration and deceleration During open loop operation, the ECU ignores information from the exhaust oxygen senso