Catalytic Converter: Service and Repair

Catalytic Converter Replacement (4.3L)

Removal Procedure





1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
2. Remove the oil pan skid plate bolts and skid plate, if equipped.
3. Remove the transmission crossmember. Refer to Transmission Support Crossmember Replacement (2WD 2500 HD/3500) Transmission Support Crossmember Replacement (2WD 1500/2500) Transmission Support Crossmember Replacement (4WD 1500/2500) Transmission Support Crossmember Replacement (4WD 2500 HD/3500) .




4. Remove the right front connector position assurance (CPA) retainer.
5. Disconnect the right front heated oxygen sensor (HO2S) electrical connector (5) from the engine wiring harness electrical connector (4).
6. Remove the right rear CPA retainer.
7. Disconnect the engine wiring harness electrical connector (2) from the right rear HO2S electrical connector (1).
8. Remove the right rear HO2S electrical connector clip from the engine harness clip (3).




9. Remove the left rear CPA retainer.
10. Disconnect the engine wiring harness electrical connector (1) from the left rear HO2S electrical connector (2).
11. Remove the left rear HO2S electrical connector clip from the frame.




12. For vehicles equipped with 2 wheel drive (2WD) perform the following steps, for vehicles equipped with 4 wheel drive (4WD) proceed to step 15.
13. Remove the left front CPA retainer.
14. Disconnect the left front HO2S electrical connector (7) from the engine wiring harness electrical connector (6).




15. For vehicles equipped with 4WD perform the following steps, remove the left front CPA retainer.
16. Disconnect the engine wiring harness electrical connector (7) from the left front HO2S electrical connector (8).
17. Remove the left front HO2S electrical connector clip from the fuel line clip (2).




18. Remove the catalytic converter to muffler nuts.




19. Remove the catalytic converter to exhaust manifold nuts (1).
20. Separate the catalytic converter assembly from the exhaust manifolds.
21. Remove the catalytic converter assembly from the exhaust muffler.
22. If replacing the catalytic converter assembly, perform the following steps, otherwise proceed to step 4 in the installation procedure.
23. Remove the exhaust seals (2 and 3).




24. Remove the HO2S (1-4) from the catalytic converter assembly.



Installation Procedure

Important: A special anti-seize compound is used on the HO2S threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from as exhaust component and if for any reason the sensor is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.







1. If replacing the catalytic converter assembly, perform the following steps, otherwise proceed to step 4.
2. If reinstalling the old sensors, coat the threads with anti-seize compound GM P/N 12377953, or equivalent.

Notice: Refer to Component Fastener Tightening Notice .

3. Install the HO2S (1-4) to the catalytic converter assembly.
Notice: Refer to Fastener Notice .



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





4. Install the NEW exhaust seals (2 and 3) as required.
5. Install the catalytic converter assembly to the muffler.
6. Install the catalytic converter assembly to the exhaust manifolds.
7. Install the catalytic converter to exhaust manifold nuts (1).

Tighten the nuts to 50 N.m (37 lb ft).





8. Install the catalytic converter to muffler nuts.

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





9. For vehicles equipped with 4WD perform the following steps, for vehicles equipped with 2WD proceed to step 13.
10. Connect the engine wiring harness electrical connector (6) to the left front HO2S electrical connector (7).
11. Install the CPA retainer.
12. Install the HO2S electrical connector clip to the fuel line clip (2).




13. For vehicles equipped with 4WD perform the following steps, connect the engine wiring harness electrical connector (7) to the left front HO2S electrical connector (8).
14. Install the left front CPA retainer.




15. Connect the engine wiring harness electrical connector (1) to the left rear HO2S electrical connector (2).
16. Install the left rear HO2S electrical connector clip to the frame.
17. Install the CPA retainer.




18. Connect the engine wiring harness electrical connector (2) to the right rear HO2S electrical connector (1).
19. Install the right rear CPA retainer.
20. Install the right rear HO2S electrical connector clip to the engine harness clip (3).
21. Connect the right front HO2S electrical connector (5) to the engine wiring harness electrical connector (4).
22. Install the right front CPA retainer.




23. Install the transmission crossmember. Refer to Transmission Support Crossmember Replacement (2WD 2500 HD/3500) Transmission Support Crossmember Replacement (2WD 1500/2500) Transmission Support Crossmember Replacement (4WD 1500/2500) Transmission Support Crossmember Replacement (4WD 2500 HD/3500) .
24. Position the oil pan skid plate and install the oil pan skid plate bolts, if equipped.

Tighten the bolts to 28 N.m (21 lb ft).

25. Lower the vehicle.