GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2009 🢒 TrailBlazer - 4WD 🢒 Preface 🢒 Dangers, Warnings, and Cautions 🢒 Body Control Module 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. Do not open the BCM housing. The module does not have any serviceable components. The module may be replaced only as an assembly.

    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 BCM on a GMC Envoy XL, remove the left second row seat. Refer to Rear Seat Replacement.
  3. If replacing the BCM 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 40-way 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: 684391 Size: SH
  10. With an upward motion, remove the BCM (1) from the rear electrical center.

Installation Procedure

    Object Number: 684391 Size: SH
  1. Index the slots on the BCM (1) to the rear electrical center.
  2. Using a downward motion, install the BCM to the rear electrical center.

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

    5. Object Number: 684396 Size: SH
  5. Connect the 40-way body wiring extension (1) to the BCM.

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

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


    Object Number: 683548 Size: SH
  7. Install the rear electrical center cover.
  8. If replacing the BCM on a Chevrolet TrailBlazer or GMC Envoy, position the left hand second seat to a passenger position.
  9. If replacing the BCM on a GMC Envoy XL, install the left second row seat. Refer to Rear Seat Replacement.
  10. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection.
  11. If installing a replacement BCM, program the BCM. Refer to Control Module References.