Oxygen Sensor: Testing and Inspection

1. Warm the engine up to normal operating temperature.
2. With the engine off, disconnect the oxygen sensor and ground the single wire connector going to the ECU. This will induce a full rich condition.

Oxygen Sensor Terminals:

3. Connect a volt meter to the single wire coming from the oxygen sensor and start the engine.
4. Watch the voltage reading. The oxygen sensor output should be 0.45 - 1.0 VDC.

a. If the reading is 0.45 - 1.0 v. oxygen sensor is functioning properly.
b. If the reading is lower than 0.45 v., replace the oxygen sensor.

Oxygen Sensor Heater Circuit


5. Disconnect the oxygen sensor heater wires at the two terminal connector.
6. Using a set of suitable jumper leads connect a volt meter to the oxygen sensor heater wires at the two terminal connector. With the ignition in the RUN position (ON) and the fuel pump relay bypassed, the voltage should be 12 volts.
7. Remove the volt meter.
8. Connect an amperage meter to the heater wires. The meter should display a 0.5 - 1.3 amp. draw. If amperage is incorrect oxygen sensor heating element is faulty, and the oxygen sensor should be replaced. If an ammeter is not available, check the heater resistance with an ohmmeter. Readings should be 3 ohms (cold) or 13 ohms (hot). If either test results are not as specified, replace the oxygen sensor.