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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 717 (ENGINE EXHAUST SYSTEM)REPAIR INSTRUCTIONSCATALYTIC CONVERTER REPLACEMENT (3.1L)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 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: The three way catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets at the front and rear flanges when servicing the three way catalytic converter. Never reinstall the original gasket.
  1. Raise and support the vehicle. Refer to LIFTING & JACKING THE VEHICLE .
  2. Disconnect the heated oxygen (HO2S) sensor wiring harness connector and retainers.
  3. Support the exhaust system.
  4. Remove the catalytic converter bolts.
  5. Remove the catalytic converter gasket.
    Fig 1: Catalytic Converter Gasket & Bolts
    G01704091Courtesy of GENERAL MOTORS CORP.
  6. Remove the exhaust manifold pipe stud nuts.
  7. Remove the three way catalytic converter.
    Fig 2: Exhaust Manifold Pipe Stud Nuts
    G01704092Courtesy of GENERAL MOTORS CORP.
  8. Remove the exhaust manifold pipe gasket.
    Fig 3: Exhaust Manifold Pipe Gasket
    G01704093Courtesy of GENERAL MOTORS CORP.
  9. Remove the heated oxygen (HO2S) sensor. Refer to HEATED OXYGEN SENSOR .
    Fig 4: Heated Oxygen (HO2S) Sensor
    G01704094Courtesy 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.