TESTING

Heated Sensor

WARNING
Do not pierce the wires when testing this sensor; this can lead to wiring harness damage. Back probe the connector to properly read the voltage of the HO2S.

1. Disconnect the HO2S.
2. Measure the resistance between PWR and GND terminals of the sensor. If the reading is approximately 6 ohms at 68°F (20°C). the sensor's heater element is in good condition.
3. With the HO2S connected and engine running, measure the voltage with a Digital Volt-Ohmmeter (DVOM) between terminals HO2S and SIG RTN (GND) of the oxygen sensor connector. If the voltage readings are swinging rapidly between 0.01–1.1 volts, the sensor is probably okay.

Non-Heated Sensor

WARNING
Do not pierce the wires when testing this sensor; this can lead to wiring harness damage. Back probe the connector to properly read the voltage of the O2S.

1. Warm up the engine and allow it to run at idle.
2. Disconnect the O2S.

   Fig. 1: Inspection of the O2S terminal voltage

3. Connect a voltmeter between the O2S and a good ground.
4. Run the engine at 4,500 rpm until the voltmeter reading indicates approximately 0.7V.
5. Increase and decrease the engine speed suddenly several times. Check to see that when the speed is increased, the voltmeter reads between 0.5V–1.0V and when the speed is decreased, the reading is between 0V–0.4V.
6. If the actual readings are out of specifications, replace the O2S.