Oxygen Sensor: Testing and Inspection

CAUTION: Before checking the Oxygen Sensor,
a. Run the engine until the engine coolant temperature has reached 185-205~F (85-95~C).
b. Use a digital voltmeter

Passenger Side Kick Panel:

1. Disconnect the Oxygen Sensor connector.

Testing The Oxygen Sensor:

2. Measure the resistance between terminals # 3 and # 4 of the oxygen sensor connector.
If the temperature is 68~F (20~C), the resistance should be approximately 12 ohms. Resistance should increase to 30 or more ohms as the exhaust temperature is increased to 752~F (400~C).

Testing The Oxygen Sensor:

3. 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.

4. Connect a digital voltmeter between terminals # 1 and # 2 of the oxygen sensor.

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

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