Catalytic Converter Replacement - Left Side LZ4

Tools Required

J 39194-B Heated Oxygen Sensor Wrench

Notice: The oxygen sensor uses a permanently attached pigtail and connector. Do not remove the pigtail from the oxygen sensor. Damage to or removal of the pigtail connector could affect proper operation of the oxygen sensor.

Notice: The use of excessive force may damage the threads in the exhaust manifold/pipe.

Important: The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the HO2S.

Important: The HO2S may be difficult to remove when the engine temperature is less than 48°C (120°F)

1. Remove the air cleaner assembly. Refer to Air Cleaner Assembly Replacement .
2. Remove the connector position assurance (CPA) retainer (5).
3. Disconnect the engine wiring harness electrical connector (4) from the heated oxygen sensor (HO2S) electrical connector (3).
4. Remove the HO2S electrical connector rosebud clip from the oil level indicator tube tab.



5. Remove the exhaust manifold heat shield bolts and shield.



6. Remove the left (front) catalytic converter nuts (1) at the exhaust manifold.
7. Remove the muffler assembly. Refer to Muffler Replacement .



8. Remove the lower right HO2S electrical connector CPA retainer (1).
9. Disconnect the rear HO2S electrical connector from the engine wiring harness electrical connector (2).



10. Remove the lower left HO2S CPA retainer (3).
11. Disconnect the front engine wiring harness electrical connector (1) from the HO2S electrical connector.



12. Remove the lower right and left HO2S's (1, 2) using the J 39194-B .



13. Remove the left (front) catalytic converter to right (rear) catalytic converter nuts (3).
14. Remove the right (rear) catalytic converter bolt (5) and nuts (1) at the exhaust manifold.
15. Remove and discard the gasket (6).
16. Remove the right (rear) catalytic converter (2).
17. Remove the left (front) catalytic converter (4).
18. Remove and discard the left (front) catalytic converter to manifold gasket.
19. Inspect the catalytic converter-to-exhaust manifold flange.

Catalytic Converter to Manifold Flange Warpage:

•	Service Limit: 0.7 mm (0.028 in) max.

•	Standard: 0.7 mm (0.028 in) max.

1. Install a NEW gasket to the left (front) catalytic converter studs.
2. Install the left (front) catalytic converter (4).
3. Install a NEW gasket (6) tothe right (rear) catalytic converter studs.
4. Install the right (rear) catalytic converter (2).

Notice: Refer to Fastener Notice in the Preface section.

5. Install the right (rear) catalytic converter bolt (5) and nuts (1) at the exhaust manifold.

Tighten
Tighten the bolt/nuts to 31 N·m (23 lb ft).

6. Install the left (front) catalytic converter to right (rear) catalytic converter nuts (3).

Tighten
Tighten the nuts to 31 N·m (23 lb ft).





Important: A special anti-seize compound is used on the HO2S threads. The compound consists of graphite suspended in fluid and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove. New or service sensors will already have the compound applied to the threads. If a sensor is removed from an engine and is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.

7. If reinstalling the old HO2S, coat the threads with anti-seize compound GM P/N 12377953 or equivalent.
8. Install the lower right and left HO2S's (1, 2) using the J 39194-B .

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




9. Connect the front engine wiring harness electrical connector (1) to the HO2S electrical connector.
10. Install the lower left HO2S CPA retainer (3).



11. Connect the rear HO2S electrical connector to the engine wiring harness electrical connector (2).
12. Install the lower right HO2S electrical connector CPA retainer (1).
13. Remove the muffler assembly. Refer to Muffler Replacement .



14. Install the left (front) catalytic converter nuts (1) at the exhaust manifold.

Tighten
Tighten the nuts to 31 N·m (23 lb ft).




15. Remove the exhaust manifold heat shield bolts and shield.

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




16. Connect the engine wiring harness electrical connector (4) to the HO2S electrical connector (3).
17. Install the CPA retainer (5).
18. Install the HO2S electrical connector rosebud clip to the oil level indicator tube tab.
19. Install the air cleaner assembly. Refer to Air Cleaner Assembly Replacement .