For 1990-2009 cars

### Removal Procedure

Caution: Refer to Heated Oxygen and Oxygen Sensor Caution in the Preface section.

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle.
2. Disconnect the engine wiring harness electrical connector (3) from the heated oxygen sensor (HO2S) electrical connector (2).
3. Remove the HO2S electrical connector retainer from the engine wiring harness clip (1).
4. Remove the HO2S (2) from the exhaust manifold.

### Installation Procedure

Note: A special anti-seize compound is used in the HO2S threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an exhaust component and if for any reason the sensor is to reinstalled, the threads must have anti-seize compound applied before the reinstallation.

1. If reinstalling the old sensor, coat the threads with anti-seize compound GM P/N 12377953, or equivalent.

Caution: Refer to Fastener Caution in the Preface section.

2. Install the HO2S (2) to the exhaust manifold.

Tighten
Tighten the sensor to 42 N·m (31 lb ft).

3. Connect the engine wiring harness electrical connector (3) to the HO2S electrical connector (2).
4. Install the HO2S electrical connector retainer to the engine wiring harness clip (1).
5. Lower the vehicle.