An oxygen sensor measures the proportion of oxygen in exhaust gases to help maintain the optimal air-fuel ratio for emissions control. It works with a three-way catalytic converter to reduce engine emissions. There are several types of oxygen sensors, including zirconia, titanium, and wide-band air-fuel ratio sensors. They function by changing voltage or resistance based on whether the air-fuel mixture is rich, lean, or stoichiometric. Maintaining proper oxygen sensor functioning is important for emissions control and engine performance.

1. AUTOMOTIVE
TECHNO
Mohammed Raqeeb Ahmed
Bangalore
Nov 2017

2. OXYGEN SENSOR

3. Oxygen sensor:
An oxygen sensor is an electronic device that measures the
proportion of oxygen(O2) in the exhaust gases.
Location:

4. •Lambda sensors are a vital part of the exhaust gas after treatment technology
used by vehicle manufacturers to reduce engine emissions
•This technology employs an oxygen sensor and three-way catalyst which
together have the ability to take the three main toxic gases produced by an
engine
•
Air Fuel Ratio
• The ideal ratio of air to fuel to achieve complete combustion is 14.7:1
this chemically correct air/fuel ratio is known as a stoichiometric ratio or
Lambda (λ) =1.0.
•A fuel rich mixture would have a lower value e.g. 0.8 and a fuel lean mixture
would have a higher value e.g. 1.2.

5. Zirconia Oxygen Sensor
The early introduction of the oxygen sensor came about in the late 1970s.

7. •Rich Mixture:
It generate up to about 0.9 volts.
•Lean Mixture:
The sensor's output voltage will drop down to about 0.1 volts.
•Balanced:
The sensor will read around 0.45 volts when the mixture is nearly to
stoichiometric ratio.
Heater
An oxygen sensor must be hot (about 600 to 650 degrees F) before it will generate
a voltage signal.
Note:
This sensor does not detect the extent of the richness or leanness. It is for
this reason that the zirconia O2 sensor is called a “narrow-band” O2 sensor.

8. Titanium Oxygen Sensor
The titania O2 sensor was used throughout the late 1980s

9. Rich mixture:
resistance of the sensor is around 950 ohms.
Lean mixture:
resistance of the sensor is above 21 kilo ohms
Supply is provided to the sensor then the change are determined by ECM.
Note:
Even this type of sensor is also a narrow band sensor
A Titanium Dioxide Element changes its electrical resistance proportionally to
the partial oxygen pressure in the gas mixture.
• With a high oxygen concentration (λ > 1) the titanium dioxide is less conductive
• With a low oxygen concentration (λ < 1) it is more conductive.

10. Air fuel Ratio Sensor

11. Pump cell current is directly proportional to oxygen in the exhaust pipe.
Condition of working:
•Rich Mixture:
The sensor produces a “negative” current that goes from zero to about
2.0 milliamps.
When lambda is 0.7 and the air/fuel ratio is near 11:1.
•Lean Mixture:
The sensor produces a “positive” current that goes from zero up to
1.5 milliamps.
•Balanced Mixture:
Sensor produces no output current.
•Operating temperature
doubled than the ordinary o2 sensor

12. Symptoms:
• Check engine
• Poor mileage
• Rough engine idle and misfire.
Replacing intervals:
•Unheated one- or two-wire O2 sensors on 1976 -1990s
changed for every 30,000 to 50,000 miles.
• Heated three and four-wire O2 sensors on 1980s -1990s
changed every 60,000 miles.
•And on 1996 and newer OBDII-equipped vehicles, the
recommended replacement interval is 100,000 miles.
Failure

13. No Of Terminal

14. Location Of Sensors

15. Error Code

16. A catalytic converter is an exhaust emission control device that converts toxic
gases and pollutants in exhaust gases from an IC Engines to less toxic
pollutants by catalyzing a redox reaction.
The main emissions from IC Engine are:
•CO
•HC
•Nox
•CO2
Carbon monoxide (CO), oxides of nitrogen (NOx) and hydrocarbons (HC) and
convert them into carbon dioxide (CO2), water H2O) and nitrogen (N2).
CATALYTIC CONVERTER