Examination
1. To check the primary sensor (upstream of the catalytic converter) connect the positive probe of the voltmeter to the signal terminal of the sensor, and the negative probe to the terminal "masses".
2. Start the engine and check that the voltage between the terminals is 0.1-0.2 volts while the engine is cold (engine running open). After about two minutes, the engine and oxygen sensor should warm up and the voltage should fluctuate between 0.1-0.9 volts (the electronic control unit has switched to the closed mode of operation).
3. Check that the resistance of the sensor heating element is 10-40 ohms. Check the voltage supply to the heating element.
4. Replace the oxygen sensor if it is defective.
Replacement
1. Disconnect the sensor connector and carefully unscrew the sensor.
2. Lubricate the threads of the new sensor before installation with an anti-corrosion agent. Installation is carried out in the reverse order of removal.