Chevrolet Citation/Omega/Phoenix/Skylark 1980-1985 Repair Guide

Oxygen Sensor

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OPERATION



An oxygen sensor is used on all 1980 models built for California 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.

REMOVAL & INSTALLATION





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Fig. Fig. 1 Oxygen sensor removal and installation



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Fig. Fig. 2 Before removing the oxygen sensor, spray a suitable lubricant on the threads (see arrow)



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Fig. Fig. 3 Let the lubricant act on the oxygen sensor threads, then use a wrench to loosen ...



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Fig. Fig. 4 ... and remove the oxygen sensor from the exhaust manifold

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 (48°C). Excessive removal force may damage the threads in the exhaust manifold or pipe; follow the removal procedure carefully.

  1. On the four cylinder engine, remove the air cleaner and the Thermac heat stove pipe, which is attached to the air cleaner case snorkel with a sheet metal screw. With the V6, raise the car to make access to the sensor easier.
  2.  
  3. Disconnect the electrical connector from the oxygen sensor.
  4.  
  5. Spray a commercial heat riser solvent onto the sensor threads and allow it to soak in for at least five minutes.
  6.  
  7. Carefully unscrew and remove the sensor.
  8.  
  9. To install, first coat the new sensor's threads with GM anti-seize compound No. 5613695 or the equivalent.
  10.  

This is not a conventional anti-seize paste. The use of a regular compound may electrically insulate the sensor, rendering it inoperative. You must coat the threads with an electrically conductive anti-seize compound.

  1. Installation torque is 30 ft. lbs. (42 Nm). Do not overtighten.
  2.  
  3. Reconnect the electrical connector. Be careful not to damage the electrical pigtail. Check the sensor boot for proper fit and installation. Install the air cleaner, if removed.
  4.  

Mileage Counter Reset


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Fig. Fig. 5 Mileage counter reset instructions

The mileage counter must only be reset after the oxygen sensor has been replaced. If the sensor is not changed at regular intervals, it will cease to monitor the exhaust gas content, resulting in incorrect interpretation of its signal by the ECM. The result will be an overly rich fuel mixture, causing stumbling, stalling, and poor fuel economy.

At 30,000 mile intervals, the word "Sensor" will appear in the speedometer face, indicating the need for oxygen sensor replacement. After the sensor has been replaced, the mileage counter may be reset as follows:

  1. Remove the instrument cluster bezel. This procedure is covered in .
  2.  
  3. Remove the instrument cluster lens.
  4.  
  5. Using an awl, punch, or other pointed tool, apply a light downward force on the detent on the outer rim of the reminder flag, until it "clicks" into place.
  6.  
  7. Install the lens and bezel.
  8.  

Do not reset the reminder flag until the sensor has been replaced. See the note at the beginning of this procedure.

 
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