GM Service Manual Online
For 1990-2009 cars only

Heated Oxygen Sensor Replacement Sensor 1

Removal Procedure

Notice: Do not remove the pigtail from either the heated oxygen sensor (HO2S) or the oxygen sensor (O2S). Removing the pigtail or the connector will affect sensor operation.

Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type.

Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged.

This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance.

The following guidelines should be used when servicing the heated oxygen sensor:

   • Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance.
   • Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
   • Ensure the sensor or vehicle lead wires are not bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.
   • Do not remove or defeat the oxygen sensor ground wire, where applicable. Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.
   • Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.

Important: The HO2S may be difficult to remove at temperatures above 48°C (120°F). Allow the engine to cool down before attempting to remove the HO2S. Use care in order to prevent any damage to the threads in the exhaust manifold.


    Object Number: 157750  Size: SH
  1. Disconnect the heated oxygen sensor (HO2S) 1 electrical connector.

  2. Object Number: 221279  Size: SH
  3. Remove the HO2S 1 (1) from the exhaust manifold.

Installation Procedure

Important: The HO2S 1 comes with an anti-seize coating on the new sensor. Take precautions in order to prevent the removal of any of the anti-seize coating prior to installation. If the sensor was removed and is being reinstalled, an anti-seize compound must be applied to the threads before installation.


    Object Number: 221279  Size: SH
  1. Install the HO2S 1 (1) to the exhaust manifold.
  2. Notice: Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

  3. Tighten the HO2S 1.
  4. Tighten
    Tighten the HO2S 1 to 40-50 N·m (29-36 lb ft).


    Object Number: 157750  Size: SH
  5. Connect the HO2S 1 electrical connector.

Heated Oxygen Sensor Replacement Sensor 2

Removal Procedure

Notice: Do not remove the pigtail from either the heated oxygen sensor (HO2S) or the oxygen sensor (O2S). Removing the pigtail or the connector will affect sensor operation.

Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type.

Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged.

This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance.

The following guidelines should be used when servicing the heated oxygen sensor:

   • Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance.
   • Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
   • Ensure the sensor or vehicle lead wires are not bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.
   • Do not remove or defeat the oxygen sensor ground wire, where applicable. Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.
   • Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.

Important: The HO2S may be difficult to remove at temperatures above 48°C (120°F). Allow the engine to cool down before attempting to remove the HO2S. Use care in order to prevent any damage to the threads in the exhaust manifold.


    Object Number: 157612  Size: SH
  1. Disconnect the heated oxygen sensor (HO2S) 2 electrical connector.
  2. Remove the HO2S 2 from the exhaust pipe.

Installation Procedure

Important: The HO2S 2 comes with an anti-seize coating on the new sensor. Take precautions in order to prevent the removal of any of the anti-seize coating prior to installation. If the sensor was removed and is being reinstalled, an anti-seize compound must be applied to the threads before installation.


    Object Number: 157612  Size: SH
  1. Install the HO2S 2 to the exhaust pipe.
  2. Notice: Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

  3. Tighten the HO2S 2.
  4. Tighten
    Tighten the HO2S 2 to 40-50 N·m (29-36 lb ft).

  5. Connect the HO2S 2 electrical connector.