Caution: Handle the oxygen sensors carefully in order to prevent damage to the component. Keep the electrical connector and the exhaust inlet end free of contaminants. Do not use cleaning solvents on the sensor. Do not drop or mishandle the sensor.

Caution: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution in the Preface section.

Note: Remove the heated oxygen sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

1. Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement.
2. Remove the connector position assurance (CPA) retainer (3).
3. Disconnect the engine harness electrical connector (2) from the heated oxygen sensor (HO2S).
4. Remove the HO2S clip (5) from the secondary air injection (AIR) check valve hose bracket.



5. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
6. Support the rear of the frame with a tall screw type jack.



7. Remove the 4 rearward frame to body bolts (1) (left side shown, right side similar).
8. Lower the screw type jack approximately 4 cm (1.5 in) but not more than 76 mm (3 inches), allowing the rear of the frame to lower.



9. Remove the HO2S.

Note: A special anti-seize compound is used on 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 components and if for any reason the sensor is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation

1. If reusing the old HO2S, 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.

Tighten
Tighten the sensor to 41 N·m (30 lb ft).




3. Raise the engine frame into position.
4. Install the 4 rearward frame to body bolts (1) (left side shown, right side similar).

Tighten
Tighten the bolts to 191 N·m (141 lb ft).




5. Remove the screw type jack.



6. Install the HO2S clip (5) to the AIR check valve hose bracket.
7. Connect the engine harness electrical connector (2) to the HO2S.
8. Install the CPA retainer (3).
9. Install the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement.