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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1601 (BODY CONTROL SYSTEM)REPAIR INSTRUCTIONSBODY CONTROL MODULE 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 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Index the slots on the BCM (1) to the rear electrical center.
    Fig 1: Removing/Installing BCM In Rear Electrical Center
    GM684391Courtesy of GENERAL MOTORS CORP.
  2. Using a downward motion, install the BCM to the rear electrical center.
  3. Connect the 24-way gray electrical connector (1) to the BCM.
    Fig 2: Disconnecting/Connecting BCM Connectors
    GM709161Courtesy of GENERAL MOTORS CORP.
  4. Connect the 32-way tan electrical connector (2) to the BCM.
  5. Connect the 40-way body wiring extension (1) to the BCM.
    Fig 3: Wiring Extension & BCM
    GM684396Courtesy of GENERAL MOTORS CORP.
  6. Engage the sliding latch fastening the BCM to the rear electrical center.

    Slide the latch outboard until the locking tab (1) is fully seated.

    Fig 4: Identifying Rear Electrical Center Locking Tab
    GM728745Courtesy of GENERAL MOTORS CORP.
  7. Install the rear electrical center cover.
    Fig 5: View Of Rear Electrical Center Cover
    GM683548Courtesy of GENERAL MOTORS CORP.
  8. If replacing the BCM on a Chevrolet TrailBlazer, GMC Envoy or Oldsmobile Bravada, position the left hand second seat to a passenger position.
  9. If replacing the BCM on a Chevrolet TrailBlazer EXT or GMC Envoy XL, install the left second row seat. Refer to SEAT BACK REPLACEMENT - REAR NO. 1 (TRAILBLAZER EXT, ENVOY XL) in Seats.
  10. Connect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Engine Electrical.
  11. If installing a replacement BCM, program the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration .
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.