Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1313 (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 2002 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Refer to FASTENER NOTICE .

Install the heated oxygen (HO2S) sensor. Refer to HEATED OXYGEN SENSOR .

Fig 1: Heated Oxygen (HO2S) Sensor
Courtesy of GENERAL MOTORS CORP.
Install a new exhaust manifold pipe gasket to the exhaust manifold pipe studs.
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.
Install and support the three way catalytic converter.
Install the exhaust manifold pipe stud nuts.
Tighten

Tighten the exhaust manifold pipe stud nuts to 35 N.m (26 lb ft).

Fig 2: Install Exhaust Manifold Pipe Gasket & Pipe Stud Nuts
Courtesy of GENERAL MOTORS CORP.
Install the catalytic converter gasket.
Install the catalytic converter bolts.
Tighten

Tighten the catalytic converter bolts to 45 N.m (33 lb ft).
Connect the heated oxygen (HO2S) sensor wiring harness connector and retainers.
Remove the support from the exhaust system.
Inspect the exhaust system for leaks and underbody contact.
Lower the vehicle.

Fig 3: Catalytic Converter Gasket, Stud Nuts & Heated Oxygen (HO2S) Sensor
Courtesy 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.