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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1628 (ENGINE EXHAUST SYSTEM)REPAIR INSTRUCTIONSCATALYTIC CONVERTER REPLACEMENT (3.8L)INSTALLATION PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Installation Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Installation Procedure
WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. Install the heated oxygen sensor (HO2S). Refer to HEATED OXYGEN SENSOR in Removal & Installation.
    NOTE: To prevent internal damage to the flexible coupling of the catalytic converter assembly, the converter must be supported. The vertical movement at the rear of the catalytic converter assembly must not exceed 6 degrees up or down.
  2. Install a new gasket to the exhaust pipe studs.
  3. Install and support the 3-way catalytic converter.
    NOTE: Refer to FASTENER NOTICE in Cautions and Notices.
  4. Install the catalytic converter nuts.

    Tighten 

    Tighten the nuts to 60 N.m (44 lb ft).

    Fig 1: Installing Catalytic Converter Nuts
    G01969209Courtesy of GENERAL MOTORS CORP.
  5. Install a new exhaust manifold pipe gasket.
  6. Install the exhaust manifold pipe stud nuts.

    Tighten 

    Tighten the nuts to 35 N.m (26 lb ft).

    Fig 2: Installing Exhaust Manifold Pipe Stud Nuts
    G01969210Courtesy of GENERAL MOTORS CORP.
  7. Install the catalytic converter hangers.
    Fig 3: Installing Catalytic Converter Hangers
    G01969211Courtesy of GENERAL MOTORS CORP.
  8. Remove the support from the exhaust system.
  9. Connect the heated oxygen sensor (HO2S) electrical connector.
  10. Inspect the exhaust system for leaks and underbody contact.
  11. Lower the vehicle.
RENDER: 1.0x

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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.