Oxygen Sensor: Testing and Inspection

1. Disconnect the Oxygen Sensor connector.

Oxygen Sensor Continuity Test:

2. Using a digital voltmeter, check for continuity between terminals # 3 and # 4 of the oxygen sensor connector.
Continuity should exist with approximately 20 ohms.

3. If continuity does not exist, replace the oxygen sensor. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.

4. Run the engine until the engine coolant temperature has reached 176~F (80~C) or higher.

Oxygen Sensor Voltage Test:

5. Apply battery voltage to the oxygen sensor. Connect the positive battery terminal to terminal # 3 of the oxygen sensor, and the negative battery terminal to terminal # 4 of the oxygen sensor.
CAUTION: If voltage is applied to the wrong terminal or a short circuit occurs, damage could result.

6. With the battery still connected, connect a digital voltmeter between terminals # 1 and # 2 of the oxygen sensor.

7. While repeatedly raising the engine rpm, note the output voltage of the oxygen sensor.
Voltage should be 0.6 to 1 volt when the air/fuel mixture is rich.

8. Replace the sensor, if the sensor fails any of the above tests.
Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES.