Oxygen sensor
1. seat connector; 2. Secondary sensor connector; 3. Case; 4. Collar; 5. First sensor
The oxygen sensor is designed to generate a signal, on the basis of which the computer determines the oxygen content in the exhaust gases and maintains the stoichiometric composition of the combustible mixture (14.7 parts air to 1 part gasoline) by changing the duration of fuel injection. Low signal (0.1V) from the sensor corresponds to a lean mixture, and a high level signal (0.9V) - enriched mixture.
On the vehicles in question, 2 oxygen sensors are installed - at the inlet and outlet of the catalytic converter. If the temperature of the sensor is below 340°C, then there is no signal from the sensor, and until the engine warms up, the sensor-computer system operates in open loop mode. If, after the engine warms up, the signal does not exceed 0.45 V at speeds above 1500 rpm, then the open-loop mode is maintained, and the default data stored in the computer memory is used for processing instead of the signal from the sensor.
Attention! When checking the sensor, it is forbidden to disconnect the flexible conductor from it, twist the wiring, and also expose the sensor to sharp mechanical stress. Do not use solvents to clean the sensor.
Examination
1. Insert the needle probes of the voltmeter into the sensor connector, on pins 3 (positive terminal of the voltmeter) and 4 (negative terminal) - in a 4-cylinder engine. Raise the front of the car. To access the second sensor connector, you will need to remove the front seat.
2. Start the engine and watch the voltmeter reading as the engine warms up. On a cold engine, the voltage should be 0.1–0.2 V. On a warm engine, the voltage should begin to fluctuate within 0.1–0.9 V (closed loop mode is activated). If the closed loop mode does not turn on, or turns on with a large delay, then replace the sensor.
3. Check the sensor heater for proper operation by measuring the resistance between the HT and B+ terminals of the connector, which should be 11-16 ohms.
4. Check for battery voltage between the B+ terminal on the computer connector side and ground (ignition must be on).
Replacement
1. Start the engine for 1-2 minutes. Disconnect the battery from the ground and raise the car.
2. Carefully disconnect the connector from the sensor and unscrew the sensor with a ring wrench with a cutout.