Catalytic Converter: Service and Repair

Catalytic Converter Replacement (6.0L and 8.1L Engines)

Removal Procedure






1. Raise and suitably support 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.

Installation Procedure

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 the sensors to 42 Nm (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 the nuts to 50 Nm (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 the nuts to 40 Nm (30 lb ft).
OR
- Install a NEW exhaust pipe clamp. Tighten the clamp to 44 Nm (33 lb ft).






14. Install the transmission support crossmember.
15. Install the transmission support crossmember bolts. Tighten the bolts to 95 Nm (70 lb ft).






16. Lower the transmission onto the transmission support.
17. Install the transmission mount to transmission support nuts. Tighten the nuts to 40 Nm (30 lb ft).
18. Remove the support from the transmission.
19. Lower the vehicle.