Body Control Systems: Service and Repair

BODY WIRING HARNESS EXTENSION REPLACEMENT - BCM

REMOVAL PROCEDURE

IMPORTANT:
^ 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.

CAUTION: Refer to Battery Disconnect Caution in Service Precautions.




1. Disconnect the negative battery cable.
2. If replacing the BCM on a Chevrolet Trailblazer EXT or GMC Envoy XL, remove the left second row seat.
3. If replacing the BCM on a Chevrolet Trailblazer, GMC Envoy or Oldsmobile Bravada, position the left hand second seat to a cargo position.
4. Remove the rear electrical center cover.




5. Press down and hold the locking tab (1).
6. Disengage the sliding latch retaining the BCM to the rear electrical center.
Slide the latch inboard until fully extended, approximately 40 mm (1.6 in).




7. Disconnect the body wiring extension (1) from the BCM.




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. 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

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




1. Using a downward motion, install the body wiring extension (1) to the rear electrical center.




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. Connect the body wiring extension (1) to the BCM.




5. Engage the sliding latch fastening the BCM to the rear electrical center. Slide the latch outboard until the locking tab (1) is fully seated.




6. Install the rear electrical center cover.
7. If replacing the BCM on a Chevrolet Trailblazer, GMC Envoy or Oldsmobile Bravada, position the left hand second seat to a passenger position.
8. If replacing the BCM on a Chevrolet Trailblazer EXT or GMC Envoy XL, install the left second row seat.
9. Connect the negative battery cable.