Catalytic Converter Replacement 6.0 L and 8.1 L Engines

Caution: In order to avoid being burned, do not service the exhaust system while it is still hot. Service the system when it is cool.

Caution: Always wear protective goggles and gloves when removing exhaust parts as falling rust and sharp edges from worn exhaust components could result in serious personal injury.

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the engine shield bolts and shield, if necessary.



3. Remove the oil pan skid plate bolts and plate, if necessary.
4. Remove the muffler. Refer to Muffler Replacement .



5. Disconnect the connector position assurance (CPA) retainers.
6. Disconnect the oxygen sensor electrical connectors (1, 2).



7. Remove the left exhaust manifold pipe nuts.



8. Remove the catalytic converter.
9. Slide the catalytic converter hanger out of the exhaust pipe hanger bracket.



10. If equipped with a 6.0 L engine, with regular production option (RPO) Y91, remove the catalytic converter.
11. Slide the catalytic converter hanger out of the exhaust pipe hanger bracket.



12. Remove the oxygen sensors if the catalytic converter is to be replaced.

Notice: When inspecting or replacing exhaust system components, make sure there is adequate clearance from all points on the underbody to prevent overheating of the floor pan and possible damage to the passenger compartment insulation and trim materials.

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.

1. If the catalytic converter was replaced, perform the following:

1.1.	Apply anti-seize compound GM P/N 12377953 or equivalent to the threads of the old oxygen sensors.

1.2.	Install the oxygen sensors.

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




2. If equipped with a 6.0 L engine, with RPO Y91, install a NEW exhaust seal to the exhaust manifold.
3. Install the catalytic converter.

Slide the catalytic converter hanger into the exhaust pipe hanger bracket.




4. Install a NEW exhaust seal to the exhaust manifold.
5. Install the catalytic converter.

Slide the catalytic converter hanger into the exhaust pipe hanger bracket.




6. Install the left exhaust manifold pipe nuts.

Tighten
Tighten the exhaust manifold pipe nuts to 50 N·m (39 lb ft).




7. Connect the oxygen sensor electrical connectors (1, 2).
8. Connect the CPA retainers.
9. Install the muffler. Refer to Muffler Replacement .



10. Install the oil pan skid plate and bolts, if necessary.

Tighten
Tighten the oil pan skid plate bolts to 20 N·m (15 lb ft).




11. Install the engine shield and bolts, if necessary.

Tighten
Tighten the engine shield bolts to 20 N·m (15 lb ft).

12. Lower the vehicle.

Catalytic Converter Replacement 4.8L and 5.3L Engines

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the engine shield bolts and shield, if necessary.



3. Remove the oil pan skid plate bolts and plate, if necessary.



4. Support the transmission with a suitable transmission jack.
5. Remove the transmission mount to transmission support nuts.
6. Raise the transmission off the transmission support.



7. Remove the transmission support crossmember bolts and nuts.
8. Remove the transmission support crossmember.



9. Unclip the oxygen sensor connection from the floor reinforcement.



10. Remove the clip from around the engine harness and the oxygen sensor pigtail.
11. Disconnect the connector position assurance (CPA) retainers.
12. Disconnect the oxygen sensor electrical connectors.



13. Unclip the oxygen sensors electrical connectors from the following:

•

Hose clip

•	Transmission crossmember

14. Disconnect the CPA retainers.
15. Disconnect the oxygen sensor electrical connectors (1, 2).



16. Remove the left exhaust manifold pipe nuts.



17. Remove the right exhaust manifold pipe nuts.



18. Remove the exhaust muffler nuts.
19. Remove the catalytic converter.



20. Remove the oxygen sensors if the catalytic converter is to be replaced.

Notice: Refer to Fastener Notice in the Preface section.




1. If the catalytic converter was replaced, perform the following:

1.1.	Apply anti-seize compound GM P/N 12377953 or equivalent to the threads of the old oxygen sensors.

1.2.	Install the oxygen sensors.

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

2. Install the catalytic convertor.



3. Install NEW exhaust manifold pipe seals to the exhaust manifolds.
4. Install the right exhaust manifold pipe nuts until sung.



5. Install the left exhaust manifold pipe nuts until snug.
6. Tighten the right and left exhaust manifold pipe nuts.

Tighten
Tighten the nuts to 50 N·m (39 lb ft).




7. Install the exhaust muffler nuts.

Tighten
Tighten the nuts to 40 N·m (30 lb ft).




8. Connect the oxygen sensor electrical connectors (1, 2).
9. Connect the CPA retainers.
10. Clip the oxygen sensors electrical connectors to the following:

•

Hose clip

•	Transmission crossmember




11. Connect the oxygen sensor electrical connectors.
12. Connect the CPA retainers.
13. Install the clip around the engine harness and the oxygen sensor pigtail.



14. Clip the oxygen sensor connection to the floor reinforcement.



15. Install the transmission support crossmember.
16. Install the transmission support crossmember bolts and nuts.

Tighten
Tighten the bolts to 95 N·m (70 lb ft).




17. Lower the transmission onto the transmission support.
18. Install the transmission mount to transmission support nuts.

Tighten
Tighten the nuts to 40 N·m (30 lb ft).

19. Remove the transmission jack.



20. Install the oil pan skid plate and bolts, if necessary.

Tighten
Tighten the bolts to 20 N·m (15 lb ft).




21. Install the engine shield and bolts, if necessary.

Tighten
Tighten the bolts to 20 N·m (15 lb ft).

22. Lower the vehicle.