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Oxygen (O2) Sensor

  1. A malfunction in the oxygen sensor circuit will set a related diagnostic trouble code. For testing procedures, see TESTS W/CODES article in this section. Use following procedure to test oxygen sensor.
  2. Start engine and warm to operating temperature. Disconnect oxygen sensor. Connect a DVOM between lead of oxygen sensor and ground. Place DVOM on the 2-volt scale. Voltmeter reading should increase to greater than .8 volt.
  3. Using another DVOM on the 20-volt scale, connect voltmeter in series between the oxygen sensor wire from ECM and positive post of battery. Reading on voltmeter connected to oxygen sensor should decrease to a low voltage (less than .3 volt).
  4. If a second DVOM is not available, install short jumper in oxygen sensor wire from ECM. Hold jumper in one hand and touch positive post of battery with other hand. This should cause oxygen sensor to produce less than .3 volt.
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