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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 368 (ENGINE EXHAUST SYSTEM)REPAIR INSTRUCTIONSCATALYTIC CONVERTER REPLACEMENT (3.8L)REMOVAL PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Removal Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Removal Procedure
WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

Important:  The 3-way catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets at the front and rear flanges when servicing the 3-way catalytic converter assembly. Never reinstall the original gasket.

Fig 1: Catalytic Converter Hangers And Gaskets
G01766104Courtesy of GENERAL MOTORS CORP.
  1. Raise and support the vehicle.
  2. Disconnect the heated oxygen sensor (HO2S) wiring harness connector and retainers. Refer to HEATED OXYGEN SENSOR
  3. Support the exhaust system.
  4. Remove the catalytic converter hangers.
  5. Remove the catalytic converter bolts.
  6. Remove the catalytic converter gasket.
  7. Remove the exhaust manifold pipe stud nuts.
  8. Remove the 3-way catalytic converter.
  9. Remove the exhaust manifold pipe gasket at the exhaust manifold pipe studs.
  10. Remove the heated oxygen sensor (HO2S). Refer to HEATED OXYGEN SENSOR
    11. Fig 2: Heated Oxygen Sensor (HO2S)
    G01766107Courtesy of GENERAL MOTORS CORP.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.