GM Full-Size Trucks 1980-1987 Repair Guide

Oxygen Sensor



See Figure 1

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Fig. Fig. 1: Oxygen sensor locations, V6 engine shown

The oxygen sensor is a spark plug-shaped device that is screwed into the exhaust manifold on V8s and into the exhaust pipe on inline sixes. It monitors the oxygen content of the exhaust gases and sends as voltage signal to the Electronic Control Module (ECM). The ECM monitors this voltage and, depending on the value of the received signal, issues a command to the mixture control solenoid on the carburetor to adjust for rich or lean conditions.

The proper operation of the oxygen sensor depends upon four basic conditions:

  1. Good electrical connections-since the sensor generates low currents, good clean electrical connections at the sensor are a must.
  3. Outside air supply-air must circulate to the internal portion of the sensor. When servicing the sensor, do not restrict the air passages.
  5. Proper operating temperatures-The ECM will not recognize the sensor signals until the sensor reaches approximately 600ºF.
  7. Non-leaded fuel-the use of leaded gasoline will damage the sensor very quickly.

Oxygen sensors are extremely sensitive to silicone. Exposure to silicone will contaminate and destroy the oxygen sensor. Be careful not to use silicone sealers or lubricants in any area such as the intake or exhaust manifolds to prevent contamination. A white colored element or tip is an indication that the oxygen sensor has been contaminated with silicone.

No attempt should be made to measure the output voltage of the sensor. The current drain of any conventional voltmeter would be enough to permanently damage the sensor. No jumpers, test leads, or other electrical connections should ever be made to the sensor. Use these tools ONLY on the ECM side of the harness connector AFTER the oxygen sensor has been disconnected.


The sensor uses a permanently attached pigtail and connector. This pigtail should not be removed from the sensor. Damage or removal of the pigtail or connector could affect the proper operation of the sensor. Keep the electrical connector and louvered end of the sensor clean and free of grease. NEVER use cleaning solvents of any type on the sensor. The oxygen sensor may be difficult to remove when the temperature of the engine is below 120ºF. Excessive force may damage the threads in the exhaust manifold or exhaust pipe.

  1. Disconnect the electrical connector and any attaching hardware.
  3. Remove the sensor.
  5. Coat the threads of the sensor with a GM anti-seize compound 5613695 or equivalent, before installation. New sensors are pre-coated with this compound.

The GM anti-seize compound is NOT a conventional anti-seize paste. The use of a regular paste may electrically insulate the sensor, rendering it useless. The threads MUST be coated with the proper electrically conductive anti-seize compound.

Install the sensor and torque to 30 ft. lbs. Use care in making sure the boot is in the correct position to avoid melting it during operation.
Connect the electrical connector and attaching hardware if used.