Oxygen Sensor: Testing and Inspection

- Connect positive lead of voltmeter to O2 sensor signal terminal (in connector). Do not disconnect electrical connector.
- Connect negative lead of voltmeter to chassis ground.
- Select 0 to 1 VDC scale on meter.
- Run engine at 2300 rpm until operating temperature is achieved.
- Read voltage on meter at 2300 rpm.
Voltage should vary between 0.3 and 0.7 VDC.
- Abruptly close throttle and observe meter while engine is slowing.
Voltage should drop below 0.2 VDC.
- Allow the engine to idle.
Voltage should vary between 0.3 and 0.7 VDC.
If voltages or fluctuation are not as specified, the O2 sensor is most likely faulty.
Check for vacuum leaks and poor electrical connections prior to replacing O2 sensor.