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.

Catalytic Converter Replacement 6.0L and 8.1L 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. Depending on which side is being replaced, perform one of the following steps:

•	Remove the exhaust muffler nuts.

•

or

•	Loosen the exhaust pipe clamp.

5. Remove the necessary exhaust system hangers so that the pipes can be separated.
6. Use a jack stand to support the exhaust.



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



9. Remove the left exhaust manifold pipe nuts.



10. 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: 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 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 the left exhaust manifold pipe nuts.

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




5. Connect the oxygen sensor electrical connectors (1, 2).
6. Connect the CPA retainers.
7. Install the exhaust pipe/catalytic converter to the vehicle.
8. Install the exhaust system hangers.



9. Depending on which side is being replaced, perform one of the following steps:

•	Install the exhaust muffler nuts.

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

•

or

•	Install a NEW exhaust pipe clamp.

Tighten
Tighten the clamp to 44 N·m (33 lb ft).




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

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




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

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

12. Lower the vehicle.