Oxygen Sensor: Testing and Inspection

Oxygen Sensor Testing:

OXYGEN SENSOR HEATER TESTING

NOTE: Use a 10 megohm digital volt/ohmmeter (DVOM) for oxygen sensor testing.

1. With ignition "OFF," disconnect three pin oxygen sensor connector.
2. With ignition "ON" and engine not running, probe white/purple wire from vehicle harness with DVOM. Meter should read battery voltage. If not, repair open in white/purple wire.
3. A test light connected between white/purple wire and black wire (ground) should light. If not, repair faulty ground.
4. Measure resistance at oxygen sensor harness between black wire and light blue wire. Resistance (varying with temperature) should be between 3-5 ohms and 14 ohms. If not, replace oxygen sensor.
5. Clear codes after completing work.

OXYGEN SENSOR TESTING

1. Thoroughly warm up engine. Engine must be operating in closed loop. This test will not be valid if oxygen sensor is too cool.
2. Unplug oxygen sensor connector. Connect DVOM between ground and sensor side of connector.
3. Install a short jumper wire in ECM side of sensor lead. While holding jumper wire in one hand, alternately touch negative battery terminal and then positive terminal with other hand.

CAUTION: Do not touch sensor lead directly to battery.

4. Monitor DVOM reading. When negative battery terminal is touched, oxygen sensor output voltage should increase (up to one volt). When positive battery terminal is touched, oxygen sensor output voltage should drop (as low as .1 volt).
5. Replace oxygen sensor if it does not respond as indicated.
6. Clear codes after completing work.