Oxygen Sensor: Testing and Inspection

1. Start engine and allow to reach normal operating temperature.
2. Disconnect oxygen sensor connector.

Fig. 15 Checking Oxygen Sensor:

3. Connect voltmeter between oxygen sensor side terminal and ground, Fig. 15. Use high quality or digital voltmeter. Do not apply any voltage to oxygen sensor.

Fig. 16 Turning Off Microswitch:

4. With engine running at 1500--2000 RPM, turn wide open throttle micro switch on, Fig. 16. Voltmeter should read about .8 volts.
5. With engine running at 1000--1500 RPM, disconnect vacuum hose at intake manifold. Voltmeter should read almost zero volts (0.2).
6. Reconnect vacuum hose and electrical connector.