Oxygen Sensor: Testing and Inspection

1. Warm up engine & run at idle.
2. Disconnect connector at O2 sensor wiring harness.
3. Attach a voltmeter between O2 sensor connector (O2 sensor side) and ground.
4. Run engine at 4000 RPM (exc. 1988 626 and MX-6) or at 4500 RPM (1988 626 and MX-6) until voltmeter indicates approximately .7 volt (1988) or approximately .55 volt (1986-87).
5. Increase and decrease engine speed suddenly several times. When speed is increased, meter should read .5-1 volt. When speed is decreased, meter should read 0-.4 volts.
6. If voltage readings are not as described, replace sensor.
7. On 1988 models, check sensitivity of oxygen sensor as follows:
a. With engine idling at operating temperature, connect system tester to check connector.
b. Increase engine speed to between 2000-3000 RPM and ensure monitor lamp flashes more than 8 times in 10 seconds.