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 704 (CELLULAR COMMUNICATION SYSTEM)REPAIR INSTRUCTIONSONSTAR® VEHICLE INTERFACE UNIT (VIU) REPLACEMENTINSTALLATION 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 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Record the 10-digit STID number from the label on the VIU module.
- Install the VIU to the bracket.
- Connect the electrical connectors.
- Install the screws (1) securing the VIU to the bracket. Tighten the screws to 9 N.m (80 lb in).
- Install the IP trim panel. Refer to TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER .
- Contact the OnStar® Dealer Support line by pressing the OnStar® button twice. The 10-digit STID number recorded will be needed by the OnStar® Dealer Support line.
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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.