By determining the composition of the exhaust gases before and after the converter, the PCM determines the efficiency of the converter.
Pic. 7.16. Location of oxygen sensors on models from 2001: 1 - electrical connectors; 2 - oxygen sensor (block 2, sensor 2); 3 - oxygen sensor (block 1, sensor 2)
Primary (in the direction of the exhaust gases) the oxygen sensor is located in the exhaust manifold or in the exhaust pipe, and the secondary is located behind the catalytic converter (pic. 7.16).
Attention! Do not confuse oxygen and air-fuel mixture sensors. They are similar in appearance, but work differently and have different performance characteristics.
Like the oxygen sensor, the air-fuel ratio sensor converts information into an output voltage that is sent to the engine control unit. The magnitude of the signal is proportional to the air/fuel mixture ratio in the exhaust gas stream. The air fuel ratio sensor changes the output voltage from 3.3V to 3.0V depending on the proportion of oxygen in the exhaust stream. Like the oxygen sensor, the air-fuel mixture sensor begins to work normally only after warming up, for which heaters are installed on the sensors.
When servicing sensors take the following precautions:
Oxygen and air-fuel ratio sensors have a permanently attached braid with wires and an electrical connector that is inseparable from the sensor. Damage to the sheath with wires or removal of her or the electrical connector may impair the performance of the sensors.
Avoid getting dirt, grease or other substances on the sensors.
Do not use solvents to clean sensors.
Do not drop or hit the sensors.
Since the sensors are installed in the exhaust manifold or tailpipe, they burn, making them very difficult to remove on a cold engine.
Replacement of oxygen sensors (O2S) produce as follows:
In order to exclude the possibility of damage to the sensors, start the engine for 1-2 minutes, then turn it off. Removing the sensors is now easier, but care must be taken not to burn yourself on the hot exhaust manifold and exhaust pipe.
Turn off the ignition and disconnect the wire «masses» from the battery.
If it is necessary to remove the secondary sensor, raise the vehicle on a lift.
Pic. 7.17. Location of the primary oxygen sensor on block 2 on models from 2001
The primary sensor can be replaced without lifting the vehicle (pic. 7.17).
Disconnect the electrical connector located on the oxygen sensor wires.
Pic. 7.18. Location of the secondary oxygen sensor on block 1 on models from 2001
Unscrew the sensor from the exhaust manifold or exhaust pipe (pic. 7.18). Use a split spanner to unscrew the sensor.
Apply a non-stick compound to the threads of the sensor to make it easier to unscrew the sensor later. The threads of the new sensor are already coated with a non-stick compound. Screw in the sensor and tighten it securely.
Connect the sensor electrical connector.
Lower the car.
Install the sensor in the reverse order of removal.