Catalytic Converter Replacement 4.3L, 4.8L, and 5.3L Engines

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle .
2. If equipped, unclip the oxygen sensor connection from the floor reinforcement.
3. Disconnect the oxygen sensor electrical connector.



4. Remove the oxygen sensor clips from the frame.
5. Disconnect the connector position assurance (CPA) retainers.
6. Disconnect the oxygen sensor electrical connectors.



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

•

Hose clip

•	Transmission crossmember

8. Disconnect the CPA retainers.
9. Disconnect the oxygen sensor electrical connectors (1, 2).



10. Remove the left exhaust manifold pipe nuts.



11. Remove the right exhaust manifold pipe nuts.



12. Remove the exhaust muffler nuts.
13. Remove the catalytic converter.



14. If necessary, remove the oxygen sensors.

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 necessary, install the oxygen sensors.

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 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 snug.



5. Install the left exhaust manifold pipe nuts until snug.
6. Tighten the 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. Connect the oxygen sensor electrical connector.
15. If equipped, clip the oxygen sensor connection to the floor reinforcement.
16. 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 .
2. Support the transmission with a suitable transmission jack.
3. Remove the transmission mount to transmission support nuts.
4. Raise the transmission off of the transmission support.



5. Remove the transmission support crossmember bolts.
6. Remove the transmission support crossmember.



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

•	Remove the exhaust muffler nuts.

•

or

•	Loosen the exhaust pipe clamp.

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



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



12. Loosen the right exhaust manifold pipe nuts.
13. Remove the left exhaust manifold pipe nuts.
14. Using the transmission jack, lower the transmission slightly.



15. Remove the catalytic converter.
16. Slide the catalytic converter hanger out of the exhaust pipe hanger bracket.



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



19. 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 sensors to 42 N·m (31 lb ft).




2. If equipped with a 6.0L 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.
7. Tighten the right exhaust manifold pipe nuts.

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

8. Using the transmission jack, raise the transmission slightly.



9. Connect the oxygen sensor electrical connectors (1, 2).
10. Connect the CPA retainers.
11. Install the exhaust pipe/catalytic converter to the vehicle.
12. Install the exhaust system hangers.



13. 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).




14. Install the transmission support crossmember.
15. Install the transmission support crossmember bolts.

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




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

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

18. Remove the support from the transmission.
19. Lower the vehicle.

Catalytic Converter Replacement 6.6L Engine

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle .
2. Support the transmission with a suitable transmission jack.
3. Remove the transmission mount to transmission support nuts.
4. Raise the transmission off of the transmission support.



5. Remove the transmission support crossmember bolts.
6. Remove the transmission support crossmember.



7. Loosen the catalytic converter coupling nuts (1).



8. Loosen the exhaust pipe clamp.
9. Slide the exhaust pipe clamp up onto the exhaust pipe.
10. Slide the catalytic converter hanger out of the insulator.



11. Gently pry up the catalytic converter coupling clip (1) (on the muffler end) in order to disengage the locator button (3) from the coupling clip.
12. Remove the catalytic converter.
13. Gently pry up the catalytic converter coupling clip (1) (on the catalytic converter end).
14. Slide the catalytic converter coupling off the catalytic converter.

1. Align the catalytic converter coupling groove to the catalytic converter locator button.
2. Install the catalytic converter coupling until the catalytic converter locator button is fully engaged by the coupling clip.
3. Position the catalytic converter.
4. Align the catalytic converter coupling groove (2) to the muffler locator button (3).
5. Install the catalytic converter until the muffler locator button is fully engaged by the coupling clip (1).



6. Apply water based lubricant to the exhaust pipe hanger bracket, in order to aid in installation.
7. Slide the catalytic converter hanger into the insulator.
8. Slide the exhaust pipe clamp down.

Notice: Refer to Fastener Notice in the Preface section.

9. Tighten the exhaust pipe clamp.

Tighten
Tighten the clamp to 15 N·m (11 lb ft).




10. Tighten both catalytic converter coupling nuts (1) until snug.
11. Once snug, tighten the catalytic converter coupling nuts to specifications.

Tighten
Tighten the nuts to 45 N·m (33 lb ft).




12. Install the transmission support crossmember.
13. Install the transmission support crossmember bolts.

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




14. Lower the transmission onto the transmission support.
15. Install the transmission mount to transmission support nuts.

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

16. Remove the support from the transmission.
17. Lower the vehicle.