GM Camaro/Firebird 1993-1998 Repair Guide

Oxygen Sensor

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OPERATION



See Figures 1 and 2

There are two types of oxygen sensors used in these vehicles. They are the single wire oxygen sensors (O2S) and the heated oxygen sensor (HO2S). The oxygen sensor is a spark plug shaped device that is threaded into the exhaust manifold and protrudes into the exhaust stream which 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 that is sent to the computer control module. The control module monitors this voltage and, depending upon the value of the signal received, issues a command to adjust for a rich or a lean condition.

Some vehicles are equipped with more than one heated oxygen sensor.



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Fig. Fig. 1: Cross-sectional view of a single-wire oxygen sensor



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Fig. Fig. 2: Cutaway view of a four-wire heated oxygen sensor

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.

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

  1. Good electrical connections. Since the sensor generates low currents, good clean electrical connections at the sensor are a must.
  2.  
  3. Outside air supply. Air must circulate to the internal portion of the sensor. When servicing the sensor, do not restrict the air passages.
  4.  
  5. Proper operating temperatures. The computer control module will not recognize the sensor-s signals until the sensor reaches about 600°F (316°C).
  6.  

TESTING



Single Wire Oxygen Sensor (O2S)
  1. Perform a visual inspection of the connector, making sure it is engaged properly and all of the terminals are straight, tight and free of corrosion.
  2.  
  3. Check the O2S sensor voltage between the terminal and ground. Voltage should be between 350-500 millivolts. If the voltage doesn-t fall within this range, the sensor is faulty.
  4.  
  5. If the voltage is within specifications, recheck the voltage after starting the engine and running until it reaches normal operating temperature. With the engine running at 1200 rpm, then voltage should vary between 100-900 millivolts. If the voltage is not varying or not within the range, the sensor is faulty.
  6.  
  7. If the voltage is within specifications, check the circuits back to the PCM for continuity.
  8.  
  9. If the sensor and circuits are functioning properly, the PCM may be faulty.
  10.  

Heated Oxygen Sensor (HO2S)

See Figure 3

  1. Visually check the connector, making sure it is engaged properly and all of the terminals are straight, tight and free of corrosion.
  2.  
  3. Detach the sensor electrical connector and check resistance between terminals C and D. Resistance should be 10-15 ohms at 79°F. If resistance is not within specifications, the sensor heater is faulty.
  4.  
  5. If resistance is within specification, check for battery positive (B+) between connector terminals C and D with the ignition ON . If battery positive (B+) is not present, check the circuit continuity back to the PCM. If the circuits are functioning properly, the PCM may be faulty.
  6.  



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Fig. Fig. 3: Heated Oxygen Sensor (HO2S) sensor circuit

  1. Check the HO2S sensor voltage between terminals A and B with the engine OFF . The voltage should be between 350-500 millivolts. If the voltage doesn-t fall within that range, the sensor is faulty.
  2.  
  3. If the voltage is within specifications, recheck the voltage after heating the engine to normal operating temperature. With the engine running at 1200 rpm, then voltage should vary between 100-900 millivolts. If the voltage is not varying or not within the range, the sensor is faulty.
  4.  
  5. If the voltage is within specifications, check the circuits back to the PCM for continuity.
  6.  
  7. If the sensor and circuits are functioning properly, the PCM may be faulty.
  8.  

REMOVAL & INSTALLATION



See Figures 4 trough 15


WARNING
The sensors use 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 proper operation of the oxygen 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 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. Disconnect the negative battery cable.
  2.  
  3. Locate the oxygen sensor. It protrudes from the exhaust manifold (it looks somewhat like a spark plug). It may be necessary to raise and safely support the vehicle to access the sensor.
  4.  



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Fig. Fig. 4: Location of the bank 1 heated oxygen sensor-1995-97 5.7L engine shown



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Fig. Fig. 5: The bank 2 heated oxygen sensor, on the 1995-97 5.7L engine, is screwed into the passenger side exhaust manifold



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Fig. Fig. 6: Location of the bank 1 HO2S 1 and bank 2 HO2S 1-1996 3.8L engine shown



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Fig. Fig. 7: Location of the bank 1 HO2S 2 and bank 1 HO2S 3-1996 3.8L engine shown



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Fig. Fig. 8: Bank 1 sensor 1 location-1998 5.7L engine



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Fig. Fig. 9: On the 1998 5.7L engine, detach the electrical connector from the bank 1 sensor 2 ...



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Fig. Fig. 10: ... then remove the bank 1 sensor 2-1998 5.7L engine



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Fig. Fig. 11: Location of the bank 2 sensor 1-1998 5.7L engine



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Fig. Fig. 12: Bank 2 sensor 2 location-1998 5.7L engine

  1. Detach the electrical connector from the oxygen sensor harness.
  2.  



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Fig. Fig. 13: Detach the oxygen sensor electrical connector

  1. Carefully remove the sensor with J 29533A or equivalent oxygen sensor socket.
  2.  



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Fig. Fig. 14: Carefully loosen the oxygen sensor. Note the preferred removal method is with the specified tool



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Fig. Fig. 15: Remove the oxygen sensor from the exhaust pipe

To install:

A special anti-seize compound is used on the oxygen sensor threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove.

  1. Coat the new sensor's threads with GM anti-seize compound No. 5613695 or the equivalent. 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.
  2.  
  3. Install the sensor and tighten it to 30 ft. lbs. (41 Nm). Do not overtighten.
  4.  
  5. Attach the electrical connector. Be careful not to damage the electrical pigtail. Check the sensor boot for proper fit and installation.
  6.  
  7. If raised, carefully lower the vehicle.
  8.  
  9. Connect the negative battery cable.
  10.  

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