Catalytic Converter Replacement LS4

Important: The catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets at the front and rear flanges when servicing the catalytic converter. Never install the original gaskets.

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
2. Disconnect the heated oxygen sensor (HO2S) electrical connector.



3. Remove the catalytic converter pipe stud nuts (2).



4. Remove the catalytic converter nuts (3).
5. Using a suitable adjustable jack, loosely support the exhaust system.



6. Remove the catalytic converter hangers (1) from the converter.
7. Remove the catalytic converter.
8. Remove and discard the catalytic converter gaskets.



9. Remove the HO2S, if required.
10. Clean and inspect the exhaust manifold and the exhaust pipe mating surfaces.

Notice: To prevent internal damage to the flexible coupling of the catalytic converter assembly, the converter must be supported. The vertical movement at the rear of the catalytic converter assembly must not exceed 6 degrees up or down.

1. Install the HO2S, if required.



2. Install NEW gaskets to the exhaust manifold and muffler studs.
3. Position the catalytic converter into place.
4. Install the catalytic converter hangers (1) to the converter.

Notice: Refer to Fastener Notice in the Preface section.




5. Install the catalytic converter pipe stud nuts (2).

Tighten
Tighten the nuts to 35 N·m (26 lb ft).




6. Install the catalytic converter nuts (3).

Tighten
Tighten the nuts to 60 N·m (44 lb ft).

7. Remove the exhaust system support.



8. Connect the HO2S electrical connector.
9. Lower the vehicle.
10. Run the vehicle and inspect the exhaust system for leaks and underbody contact.

Catalytic Converter Replacement RPOs LZE/LZ4/LZ9

Important: The catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets at the front and rear flanges when servicing the catalytic converter. Never install the original gasket.

1. Remove the intake manifold cover. Refer to Intake Manifold Cover Replacement or Intake Manifold Cover Replacement .
2. Remove the connector position assurance (CPA) retainer (3).
3. Remove the heated oxygen sensor (HO2S) electrical connector clip (1) from the ignition coil bracket.
4. Disconnect the HO2S electrical connector (2).



5. Remove the exhaust manifold heat shield bolts.
6. Remove the exhaust manifold heat shield.
7. Remove the upper catalytic converter to exhaust manifold nut (1).



8. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
9. Remove the CPA retainer (1).
10. Disconnect the HO2S electrical connector (3).



11. Remove the HO2S. Refer to Heated Oxygen Sensor 2 Replacement for the 3.5L engine.

or

Heated Oxygen Sensor 2 Replacement for the 3.9L engine.

12. Support the exhaust system.



13. Remove the catalytic converter to muffler nuts.



14. Remove the catalytic converter insulators (1).



15. Remove the catalytic converter lower nut (3).
16. Reposition the muffler assembly rearward until the catalytic converter can be removed.
17. Remove the catalytic converter (3).
18. Remove the catalytic converter gasket (2).
19. Clean and inspect the exhaust manifold and the exhaust pipe gasket mating surfaces.

1. Install the catalytic converter gasket (2) onto the catalytic converter.
2. Reposition the muffler assembly rearward until the catalytic converter can be installed.
3. Install the catalytic converter (3).

Notice: Refer to Fastener Notice in the Preface section.

4. Install the catalytic converter lower nut (3).

Tighten
Tighten the nut to 35 N·m (26 lb ft).




5. Install the catalytic converter insulators (1).



6. Install the catalytic converter to muffler nuts (3).

Tighten
Tighten the nuts to 60 N·m (44 lb ft).

7. Remove the support from the exhaust system.



8. Install the HO2S. Refer to Heated Oxygen Sensor 2 Replacement for the 3.5L engine.

or

Heated Oxygen Sensor 2 Replacement for the 3.9L engine.




9. Connect the HO2S electrical connector (3).
10. Install the CPA retainer (1).
11. Lower the vehicle.
12. Install the upper catalytic converter to exhaust manifold nut (1).

Tighten
Tighten the nut to 35 N·m (26 lb ft).




13. Install the exhaust manifold heat shield.
14. Install the exhaust manifold heat shield bolts.

Tighten
Tighten the nuts to 10 N·m (89 lb in).




15. Connect the HO2S electrical connector (2).
16. Install the connector position assurance (CPA) retainer (3).
17. Install the heated oxygen sensor (HO2S) electrical connector clip (1) to the ignition coil bracket.
18. Install the intake manifold cover. Refer to Intake Manifold Cover Replacement or Intake Manifold Cover Replacement .