GM Service Manual Online
For 1990-2009 cars only

Heated Oxygen Sensor Replacement Pre Catalytic Converter

Removal Procedure

Notice: The oxygen sensor uses a permanently attached pigtail and connector. Do not remove the pigtail from the oxygen sensor. Damage to or removal of the pigtail connector could affect proper operation of the oxygen sensor.

Notice: The use of excessive force may damage the threads in the exhaust manifold/pipe.

Important: The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the oxygen sensor.

Important: The oxygen sensor may be difficult to remove when the engine temperature is less than 48°C (120 °F).


    Object Number: 746055  Size: SH
  1. Remove the exhaust manifold heat shield. Refer to Exhaust Manifold Replacement in Engine Exhaust.

  2. Object Number: 412121  Size: SH
  3. Disconnect the oxygen sensor harness connector.
  4. Remove the oxygen sensor.

Installation Procedure

    Important: 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. New or service sensors will have the compound applied to the threads. If a sensor is removed and is to be reinstalled, the threads must have an anti-seize compound applied before installation.

  1. Coat the threads of the oxygen sensor with anti-seize compound, if necessary.

  2. Object Number: 412121  Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Install the oxygen sensor.
  4. Tighten
    Tighten the oxygen sensor to 30 N·m (22 lb ft).

  5. Connect the oxygen sensor harness connector.

  6. Object Number: 746055  Size: SH
  7. Install the exhaust manifold heat shield. Refer to Exhaust Manifold Replacement in Engine Exhaust.

Heated Oxygen Sensor Replacement Post Catalytic Converter

Removal Procedure

Notice: The Heated Oxygen Sensors each use a permanently attached pigtail and connector. This pigtail should not be removed from the heated oxygen sensor. Damage or removal of the pigtail or connector could affect proper operation of the heated oxygen sensor.

Important: Take care when handling the rear heated oxygen sensor (HO2S 2). The in-line connector and louvered end must be kept free of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the HO2S 2.


    Object Number: 10975  Size: SH
  1. Turn OFF the ignition.
  2. Disconnect the HO2S 2 connector, in the Engine Compartment.
  3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Notice: The use of excessive force may damage the threads in the exhaust manifold/pipe.

  5. Carefully remove the HO2S 2.

Installation Procedure

Important: A special anti-seize compound is used on the HO2S 2 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. New or service sensors already have the compound applied to the threads. If the sensor is removed and is to be reinstalled, the threads must be coated with an anti-seize compound before reinstallation.


    Object Number: 10975  Size: SH
  1. Coat the threads only of the HO2S 2 with anti-seize compound, if necessary.
  2. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Install the HO2S 2.
  4. Tighten
    Tighten the HO2S 2 to 41 N·m (30 lb ft).

  5. Lower the vehicle.
  6. Reconnect the HO2S 2 connector, in the engine compartment.