GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2009 🢒 TrailBlazer - 4WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Body Control Module Body Wiring Harness Extension Harness Replacement

Removal Procedure

Note: 

   • The ignition switch should be in the OFF position when connecting or disconnecting the connectors to the body control module (BCM).
   • Always disconnect the 40-way body wiring extension FIRST, the 32-way tan connector SECOND and the 24-way gray electrical connector LAST.
   • Always connect the 24-way gray electrical connector FIRST, the 32-way tan connector SECOND and the 40-way body wiring extension LAST.
   • The BCM can set DTCs with the ignition switch in the OFF position. The BCM has battery run down protection for the courtesy lamp circuit. The BCM battery run down protection cannot detect shorts on inputs or other circuits which the BCM does not control. Use the scan tool in order to activate the POWER DOWN NOW mode. Use the POWER DOWN NOW mode in order to check for current draws on circuits that are not controlled by the BCM, or controlled by the battery run down protection system.
   • Do not touch the exposed electrical contacts of the body wiring extension.

    Warning: Refer to Battery Disconnect Warning in the Preface section.

  1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection.
  2. If replacing the body wiring harness extension on a GMC Envoy XL, remove the left second row seat. Refer to Rear Seat Replacement.
  3. If replacing the body wiring harness extension on a Chevrolet TrailBlazer or GMC Envoy, position the left hand second seat to a cargo position.

    4. Object Number: 683548 Size: SH
  4. Remove the rear electrical center cover.

    5. Object Number: 728745 Size: SH
  5. Press down and hold the locking tab (1).
  6. Disengage the sliding latch retaining the BCM to the rear electrical center.

    7. Slide the latch inboard until fully extended, approximately 40 mm (1.6 in).


    Object Number: 684396 Size: SH
  7. Disconnect the body wiring extension (1) from the BCM.

    8. Object Number: 709161 Size: SH
  8. Disconnect the 32-way tan electrical connector (2) from the BCM.
  9. Disconnect the 24-way gray electrical connector (1) from the BCM.

    10. Object Number: 836844 Size: SH
  10. With an upward motion, disconnect the body wiring extension (1) from the rear electrical center.
  11. Remove the body wiring extension from the vehicle.

Installation Procedure

    Note: Ensure the sliding latch is fully extended before connecting the body wiring extension to the rear electrical center.


    Object Number: 836844 Size: SH
  1. Using a downward motion, install the body wiring extension (1) to the rear electrical center.

    2. Object Number: 709161 Size: SH
  2. Connect the 24-way gray electrical connector (1) to the BCM.
  3. Connect the 32-way tan electrical connector (2) to the BCM.

    4. Object Number: 684396 Size: SH
  4. Connect the body wiring extension (1) to the BCM.

    5. Object Number: 728745 Size: SH
  5. Engage the sliding latch fastening the BCM to the rear electrical center.

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


    Object Number: 683548 Size: SH
  6. Install the rear electrical center cover.
  7. If replacing the body wiring harness extension on a Chevrolet TrailBlazer or GMC Envoy, position the left hand second seat to a passenger position.
  8. If replacing the body wiring harness extension on a GMC Envoy XL, install the left second row seat. Refer to Rear Seat Replacement.
  9. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection.