Catalytic Converter Replacement With LU3

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.



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.

Note: 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.

Caution: Refer to Fastener Caution in the Preface section.

3. Install the HO2S (1-4) to the catalytic converter assembly and tighten 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) and tighten to 50 N·m (37 lb ft).



8. Install the catalytic converter to muffler nuts and tighten 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.
24. Position the oil pan skid plate and install the oil pan skid plate bolts, if equipped and tighten to 28 N·m (21 lb ft).
25. Lower the vehicle.

Catalytic Converter Replacement With V8 Engine

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.



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



9. Remove the left rear CPA retainer (1).
10. Disconnect the left rear HO2S electrical connector from the engine wiring harness electrical connector (3).



11. For vehicles equipped with a 4L60-E/4L70-E automatic transmission perform the following steps, for vehicles equipped with a 6L80-E automatic transmission proceed to step 15.
12. Remove the left front CPA retainer.
13. Disconnect the engine wiring harness electrical connector (2) from the left front HO2S.
14. Remove the left front HO2S electrical connector clip (1) from the fuel line clip.



15. Remove the left front CPA retainer (2).
16. Remove the engine wiring harness electrical connector clip (1) from the fuel line clip.
17. Disconnect the engine wiring harness electrical connector (3) from the left front HO2S.



18. If the vehicle is a 1500 series, remove the catalytic converter to muffler nuts.



19. If the vehicle is a 2500/3500 series, remove the muffler to catalytic converter nuts.
20. Remove the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1.



21. Remove the catalytic converter to exhaust manifold nuts (1). (1500 series shown, 2500/3500 series similar).
22. Separate the catalytic converter assembly from the exhaust manifolds.
23. Remove the catalytic converter assembly from the exhaust muffler.
24. If replacing the catalytic converter assembly, perform the following steps, otherwise proceed to step 4 in the installation procedure.
25. Remove the exhaust seals (2 and 3).



26. Remove the HO2S (1-5) from the catalytic converter assembly. (1500 series shown, 2500/3500 series similar).

Note: 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.

Caution: Refer to Fastener Caution in the Preface section.

3. Install the HO2S (1-5) to the catalytic converter assembly. (1500 series shown, 2500/3500 series similar) and tighten to 42 N·m (31 lb ft).



4. Install the NEW exhaust seals (2 and 3) as required. (1500 series shown, 2500/3500 series similar).
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) and tighten to 50 N·m (37 lb ft).
8. Install the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1.



9. If the vehicle is a 2500/3500 series, install the muffler to catalytic converter nuts and tighten to 45 N·m (33 lb ft).



10. If the vehicle is a 1500 series, install the catalytic converter to muffler nuts and tighten to 45 N·m (33 lb ft).



11. For vehicles equipped with a 4L60-E/4L70-E automatic transmission perform the following steps, for vehicles equipped with a 6L80-E automatic transmission proceed to step 13.
12. Install the HO2S electrical connector clip (1) to the fuel line clip.
13. Connect the engine wiring harness electrical connector (2) to the HO2S.
14. Install the CPA retainer.



15. Connect the engine wiring harness electrical connector (3) to the HO2S.
16. Install the engine wiring harness electrical connector clip (1) to the fuel line clip.
17. Install the CPA retainer (2).



18. Connect the left rear HO2S electrical connector to the engine wiring harness electrical connector (3).
19. Install the left rear CPA retainer (1).



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



25. Install the transmission crossmember. Refer to Transmission Support Crossmember Replacement.
26. Position the oil pan skid plate and install the oil pan skid plate bolts, if equipped and tighten to 28 N·m (21 lb ft).
27. Lower the vehicle.

Catalytic Converter Replacement With LMM

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. Remove the catalytic converter to particulate filter nuts.



8. Loosen the turbocharger exhaust pipe to catalytic converter clamp.
9. Slide the clamp up onto the turbocharger exhaust pipe.
10. Remove the catalytic converter.

1. Apply water based lubricant to the exhaust pipe hanger bracket, in order to aid in installation.
2. Install the catalytic converter.
3. Slide the down turbocharger exhaust pipe to catalytic converter clamp.

Caution: Refer to Fastener Caution in the Preface section.

4. Tighten the turbocharger exhaust pipe to catalytic converter clamp to 12 N·m (106 lb in).



5. Install the catalytic converter to particulate filter nuts and tighten to 45 N·m (33 lb ft).



6. Install the transmission support crossmember.
7. Install the transmission support crossmember bolts and tighten to 95 N·m (70 lb ft).



8. Lower the transmission onto the transmission support.
9. Install the transmission mount to transmission support nuts and tighten to 40 N·m (30 lb ft).
10. Remove the support from the transmission.
11. Lower the vehicle.