PLAYING WITH FIREPlaying with Fire is                                                                                     ...
Playing with Fire is Changing a Solenoid Because of a Solenoid Code                                                     Fi...
continue the diagnoses as you would                                                   cal solenoid code except for the EPC...
Playing with Fire is Changing a Solenoid Because of a Solenoid Code     First start with the battery. With the key on,engi...
As a dedicated transmission professional Rick Basta, owner of Transmission Kings, knows the secret to a successful shop is...
Solenoid Performance Codes
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Solenoid Performance Codes

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This article explains the difference between solenoid performance codes and circuit or electrical codes.

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Solenoid Performance Codes

  1. 1. PLAYING WITH FIREPlaying with Fire is by Jon RodriguezBecause of aSolenoid CodeW elcome to another edition of Playing with Fire. Instead of discussing interchange,we’re going to go over solenoid codediagnostics. It’s an all-to-common occurrencefor a solenoid to be replaced becausethe code definition contains the word“solenoid”… and then have the codecome back, because the root cause ofthe failure wasn’t the solenoid at all. We’re going to go over the differ-ences between performance codes andelectrical codes, and see how to diag-nose them properly before replacing asolenoid. Figure 1Performance Codes ing across any solenoid code is to look circuit. Just about every manufacturer has up the code definition in your repair How do you test a solenoid mechan-solenoid performance codes. A solenoid manuals or software. The criteria the ically? Depending on the solenoid, youperformance code might as well be computer looks for when setting the may have to use special testing equip-a ratio code; it means the solenoid is code will be listed in the definition or ment that checks solenoid flow usingworking properly electrically, accord- diagnostic tree. air or fluid. Remember, you’re check-ing to the computer. If the code is ratio-related, you ing the solenoid’s mechanical opera- What isn’t working properly are only need to check the solenoid for tion. On other solenoids, applying regu-the results of the solenoid’s operation; mechanical operation: Resistance or lated air through the working end of thethe gear it’s responsible for is slipping other electrical tests aren’t necessary if solenoid with a rubber tipped blow gunor missing. The computer identifies there aren’t any electrical codes pres- will work (figure 1).this performance problem through the ent. The vehicle’s computer has a built- When checking an on/off solenoid,speed sensors, so the condition may or in ammeter that constantly checks the energizing the solenoid will either openmay not be accompanied by gear ratio solenoid during vehicle operation, so or close the valve inside, and either stoperror codes. it’ll set an electrical code if it detects flow or let it come through. You’re just An important first step when com- an electrical problem in the solenoid looking for a change of state.14 GEARS April 2009
  2. 2. Playing with Fire is Changing a Solenoid Because of a Solenoid Code Figure 2 Figure 3 Pulse Width Modulated(PWM) solenoids require spe-cial equipment to provide theduty-cycled control signal andmeasure the solenoid’s flow char-acteristics. What it comes down to isthis: Solenoid performance codesare only rarely caused by a faultysolenoid. More often they’recaused by another part of the sys-tem; replacing the solenoid won’thelp. So how can you determinewhat’s causing the code? The first step whendiagnosing a performance code isto test drive the car and see whatgear seems to missing or slipping.A clutch-and-band applicationchart will help guide you to thecomponent that’s responsiblefor the missing or slipping gear.After you have an idea of whatcomponent is causing the slip, Figure 416 GEARS April 2009
  3. 3. continue the diagnoses as you would cal solenoid code except for the EPCfor an internal problem. (Check band Voltage Supply and Pressure Switch Manifold, becauseadjustments, air check individual Start by logging on to www.atra. they’re on their own circuits. When allcomponents, check fluid and sump com and print out a copy of bulletin the codes are set at the same time, it’scondition, etc.) #1244. The bulletin pertains to solenoid safe to jump straight to a power supply electrical codes in GM Rear Wheel diagnosis.Electrical Codes Drive Vehicles being caused by Ignition You’ll notice several areas circled The computer will set a solenoid switch issues. on the diagrams in the bulletin. Theseelectrical code if it measures incor- Sometimes the computer will set are points for testing. For these testsrect amperage in the circuit, or sees an every code for each solenoid that’s you’ll need a quality multimeter; notimproper inductive spike when operat- powered by the E wire; other times it a test light. A test light won’t working the solenoid. The amperage that a will only set one code. The computer because a drop of as little as one voltsolenoid draws is based on the amount sometimes will set one electrical code can cause the code or codes to set. Aof voltage being supplied to the sole- and then go into limp and not monitor test light can only tell you if power isnoid, divided by the amount of resis- the rest of the solenoids. Other times, present; not whether it’s low.tance in the solenoid. That’s Ohm’s you’ll get lucky and have every electri-Law (figure 2). In an ideal situation, the codewould indicate an existing problem(hard code); checking the resistancewith your multimeter would reveal theproblem instantly, and changing thesolenoid would eliminate the code.Those are the easy ones. The harderones are the codes that come and go,or aren’t caused by the solenoid at all.We’re going to go over those types ofproblems. In most applications, all threedomestic manufacturers use a systemthat provides power to all of the sole-noids from a common source. The com-puter grounds the solenoids to operatethem, and monitors amperage from theground side of the circuit. Which leavestwo things that can go wrong: 1. A problem with the voltage supply to the solenoids (ignition switch, fuse, battery, etc.) 2. An open or shorted signal wire from the computer to the solenoid. We’re going to refer to ATRATechnical Bulletin #1244. The bulletinprovides all of the wiring schematicsfor Chevrolet and GMC trucks with a4L60E, from 1993 to 2006, and high-lights the points of interest when deal-ing with power supply issues. Rear wheel drive GM pickups area good vehicle to use for going overthese diagnoses because of the numberof switch issues that can cause solenoidcodes. Keep in mind that Ford andChrysler have a slightly different wayof supplying power, but you can usethe same approach to diagnose thosevehicles.GEARS April 2009 17
  4. 4. Playing with Fire is Changing a Solenoid Because of a Solenoid Code First start with the battery. With the key on,engine off (KOEO), measure and record batteryvoltage; that’s your system voltage value. A newbattery should provide a no-load voltage of 12.6volts. Use the chart in figure 3 to determine thecondition of the battery. If the battery is outsidelimits, substitute or replace the battery with agood one. Now that you have your system voltagevalue, backprobe the transmission harness con-nector and measure the voltage supply. If it’sbelow system voltage, work your way back tothe voltage source until your voltage rises towithin 0.1 volts of the system voltage. The resistance is hiding between this lastmeasurement and the previous one. If it’s at aconnector, it’s most likely inside where the cop-per wire is crimped to the terminal. You may seegreen or white corrosion on the copper; that’sall it takes to throw the system off. Clean and Figure 5retest; in some cases you may have to replacethe connector. On GMs, it’s common for the ignitionswitch to wear and add resistance to the circuit.Here’s a shortcut for testing the ignition switch: 1. Remove the fuse that provides power to the transmission. In GM trucks, it’s located in the fuse compartment on the driver’s side dash (figure 4). 2. Set your multimeter to DC volts. 3. With KOEO, connect the positive meter lead to the fuse clip that has voltage with the fuse removed. 4. Connect the negative meter lead to the negative battery terminal. 5. Set the parking brake to keep the car from rolling. 6. Place the transmission selector lever into reverse so the engine won’t start when you turn the key. 7. Slowly move the ignition switch through its Figure 6 positions: ACC, RUN, and START — and work it back and forth. a circuit problem between the computer and the solenoid, or a bad computer. A faulty ignition switch will cause the voltage readings A quick test to eliminate the computer is to perform ato fluctuate as the corroded contacts in the switch make and solenoid bypass test: connecting a known-good solenoid withbreak connection. A good switch will have less than 0.10 volts the same resistance as the solenoid in question, and wiring itfluctuation during this test. directly to the computer (figure 6). Another quick test to see if the power supply is causing The computer has no way of knowing the solenoid isthe codes is to connect a fused jumper wire from the positive wired in at the computer, or if the solenoid even belongs tobattery terminal to the E wire, as close to the transmission that transmission. It just has to be the same resistance andconnector as possible (figure 5). This will bypass the rest have a good power supply. If the code returns, the problem isof the circuit; if the codes don’t return with the jumper con- either in the short amount of wiring between the computer andnected, you know it’s because of a problem in the power feed the test solenoid, or the computer itself.circuit. Even though we focused on GMs for this article, the Keep in mind that you won’t be able to turn the engine off procedures and electrical theory we discussed can be used onuntil you disconnect the jumper wire from the E wire. several vehicles that comes into your shop, and will help you If connecting the jumper wire does not eliminate the conquer the toughest solenoid electrical problems that comecode(s), chances are you’re dealing with a bad solenoid, your way.18 GEARS April 2009
  5. 5. As a dedicated transmission professional Rick Basta, owner of Transmission Kings, knows the secret to a successful shop is dependable performance and satisfied customers. That’s why he rebuilds with TransTec®. No surprises. Buy a TransTec® kit and you “MY GUYS can bet the bank that all the parts required for the job are there and that they all fit. It’s ALWAYS REQUEST no accident; our engineering department, product development and technical staffs, plus a proven QA system, combine to give TRANSTEC®.” you the assurance you can’t get anywhere Rick Basta, else. Owner of Transmission Kings Manufactured to meet the strictest OE Cleveland, OH standards, TransTec® kits contribute to a faster rebuild with virtually no comebacks. And detailed technical inserts reinforce what the technicians learn at various seminars. These are just a few reasons why transmis- sion rebuilders request “the kit in the gold and black bag”. TransTec® kits are produced by Freuden- berg-NOK™, the American partnership with more than $6 billion in resources. Yet it is the close, personal support that impresses transmission shops like Rick’s. TransTec® makes it easy.A Division of Freudenberg-NOK

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