1. Remove the engine sight cover. Refer to Upper Intake Manifold Sight Shield Replacement in Engine Mechanical - 6.0L.

Notice: Refer to Excessive Force and Oxygen Sensor Notice in the Preface section.

2. Remove the bank 1, sensor 1 oxygen sensor from the exhaust manifold. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 in Engine Controls - 6.0L.
3. Remove the spark plugs. Refer to Spark Plug Replacement in Engine Controls - 6.0L.
4. Remove the generator, if needed. Refer to Generator Replacement in Engine Electrical.
5. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.



6. Remove the catalytic convertor. Refer to Catalytic Converter Replacement in Engine Exhaust.
7. Lower the vehicle.
8. Remove the exhaust manifold bolts.

Important: It maybe necessary to remove the heat assembly from the exhaust manifold to gain enough clearance to remove the exhaust manifold.

9. Remove the exhaust manifold.

Important: Tighten the exhaust manifold bolts as specified in the service procedure. Improperly installed and/or leaking exhaust manifold gaskets may effect vehicle emissions and/or On-Board Diagnostics (OBD) II system performance.

1. Raise the vehicle.

Important: In the following service procedure, position the catalytic convertor on the intermediate pipe, but DO NOT tighten the clamp. Leave it loose to allow the alignment of the exhaust manifold on the cylinder head.

2. Install the catalytic convertor.
3. Lower the vehicle.
4. Apply a 5 mm (0.2 in) wide band of threadlock GM P/N 12345493 (Canadian P/N 10953489), or equivalent to the threads of the exhaust manifold bolts.



5. Position the exhaust manifold and a NEW gasket into place.
6. Install the exhaust manifold bolts.

Tighten

1. Tighten the exhaust manifold bolts a first pass to 15 N·m (11 lb ft). Tighten the exhaust manifold bolts beginning with the center 2 bolts. Alternate from side-to-side, working toward the outside bolts.
2. Tighten the exhaust manifold bolts a final pass to 25 N·m (18 lb ft). Tighten the exhaust manifold bolts beginning with the center 2 bolts. Alternate from side-to-side, working toward the outside bolts.
7. Install the bank 1, sensor 1 oxygen sensor in the exhaust manifold oxygen sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 in Engine Controls - 6.0L.
8. Install the spark plugs. Refer to Spark Plug Replacement in Engine Controls - 6.0L.
9. Install the generator. Refer to Generator Replacement in Engine Electrical.
10. Install the engine sight cover. Refer to Upper Intake Manifold Sight Shield Replacement in Engine Mechanical - 6.0L.
11. Raise the vehicle.
12. Install the catalytic convertor to exhaust manifold nuts.

Tighten
Tighten the exhaust manifold nuts to 20 N·m (15 lb ft).

13. Tighten the exhaust clamps for the catalytic convertor.

Tighten
Tighten the exhaust clamps for the catalytic convertor bolt to 20 N·m (15 lb ft).

14. Lower the vehicle.