GM Cadillac 1967-1989 Repair Guide

Oxygen Sensor


Some early models may include a maintenance reminder flag connected to the odometer which becomes visible in the instrument cluster at regular intervals, signaling the need for oxygen sensor replacement. To reset the maintenance warning flag, remove the lower steering column cover. The sensor reset cable is located to the left of the speedometer cluster. Pull on the sensor reset cable lightly to reset. Reinstall the lower steering cover.

An oxygen sensor is used on all 1980 models built for Calif. and on all 1981 and later models. The sensor protrudes into the exhaust stream and monitors the oxygen content of the exhaust gases. The difference between the oxygen content of the exhaust gases and that of the outside air generates a voltage signal to the ECM. The ECM monitors this voltage and, depending upon the value of the signal received, issues a command to adjust for a rich or a lean condition.

No attempt should ever be made to measure the voltage output of the sensor. The current drain of any conventional voltmeter would be such that it would permanently damage the sensor. No jumpers, test leads or any other electrical connections should ever be made to the sensor. Use these tools ONLY on the ECM side of the wiring harness connector AFTER disconnecting it from the sensor.


See Figures 1, 2 and 3

The oxygen sensor must be replaced every 30,000 miles (48,000 km). The sensor may be difficult to remove when the engine temperature is below 120°F (49°C). Excessive removal force may damage the threads in the exhaust manifold or pipe; follow the removal procedure carefully.

  1. Locate the oxygen sensor. On the V8 engines, it is on the front of the left side exhaust manifold, just above the point where it connects to the exhaust pipe. On the V6 engines, it is on the inside of the exhaust pipe where it bends toward the back of the car.

On the V6 engine you may find it necessary to raise the front of the car and remove the oxygen sensor from underneath.

  1. Trace the wires leading from the oxygen sensor back to the first connector and then disconnect them (the connector on the V6 engine is attached to a bracket mounted on the right, rear of the engine block, while the connector on the V8 engine is attached to a bracket mounted on the top of the left side exhaust manifold).
  3. Spray a commercial heat riser solvent onto the sensor threads and allow it to soak in for at least five minutes.
  5. Carefully unscrew and remove the sensor.

To install:
  1. First coat the new sensor's threads with G.M. anti-seize compound no. 5613695 or the equivalent.

The G.M. 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.

  1. Installation torque is 30 ft. lbs. (42 Nm.). Do not overtighten.
  3. Reconnect the electrical connector. Be careful not to damage the electrical pigtail. Check the sensor boot for proper fit and installation.

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Fig. Fig. 1: Oxygen sensor assembly - sensor screws into exhaust manifold

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Fig. Fig. 2: Oxygen sensor assembly mounting

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Fig. Fig. 3: Removing the oxygen sensor