Contents: Front Oxygen Sensor ⤓ Rear Oxygen Sensor ⤓
The heated oxygen sensor detects the oxygen concentration in the exhaust gases and converts it into a voltage, which it transmits to the engine control unit (ECU).
Front Oxygen Sensor
1. Disconnect the connector from the oxygen concentration sensor and connect a special tool (test wire harness) to the connector on the sensor side (Fig. 7.6).
Fig. 7.6. Location of the oxygen concentration sensor
2. Make sure that the circuit is closed between contact 1 (red terminal of the test lead harness) and contact 3 (blue terminal of the test lead harness) of the front oxygen concentration sensor connector (the resistance between the contacts is 4.5-8.0 Ohm at a temperature of 20°C) (Fig. 7.7).
Fig. 7.7. Checking the conductivity between the contacts of the oxygen concentration sensor connector
3. If there is no conductivity, replace the oxygen concentration sensor.
4. Start and warm up the engine to a temperature of over 80°C.
5. Using alligator clip wires, connect pin 1 of the connector (red clip) to the positive terminal of the battery, and pin 3 of the connector (blue clip) to the negative terminal of the battery (Fig. 7.8). Be very careful when connecting the wires to the battery terminals, as incorrectly connecting the wires may damage the oxygen concentration sensor.
Fig. 7.8. Using the jumper wires to test the oxygen concentration sensor
6. Connect the digital voltmeter to pins 2 (black clip) and 4 (white clip).
7. By changing the engine crankshaft speed, measure the output voltage of the oxygen concentration sensor.
Oxygen concentration sensor output voltage: 0.6-1.0V
8. If the sensor output voltage differs from the required one, replace the sensor.
Rear Oxygen Sensor
1. Disconnect the connector from the rear oxygen concentration sensor and connect a special tool (test wire harness) to the connector on the sensor side (Fig. 7.9).
Fig. 7.9. Location of the rear oxygen concentration sensor
2. Make sure that the circuit between contact 3 and contact 4 of the oxygen concentration sensor connector is closed (the resistance between the contacts is 11-18 Ohms at a temperature of 20°C) (Fig. 7.10).
Fig. 7.10. Checking the conductivity between the contacts of the rear oxygen concentration sensor connector.
3. If there is no continuity, replace the oxygen sensor. If the MUT-II does not display the nominal values, despite the fact that previous resistance checks and the condition of the wiring showed full serviceability, replace the oxygen sensor.