GM 19370406
Body Control Module

First take out the trim panel from the end gate to reach the rear body control module (BCM). Locate and unscrew the two fasteners holding the rear BCM to the end gate then detach all its electrical connections. Insert the new rear BCM into the end gate and link all electrical connectors to the module. Secure the rear BCM using its two mounting screws when you put them back into position at the end gate slot. Tighten them to 2.5 N.m (22 lb in). Refasten the trim panel into its original position on the end gate.

Ensure the Ignition Switch is off when working with Body Control Module (BCM) connectors. You should begin by detaching the negative Battery Cable and proceed with removing the left second row seat when working on a chevrolet trailblazer ext or gmc envoy xl. For a chevrolet trailblazer or gmc envoy, position the left second seat to its cargo position. To unplug the bcm gently rotate the sliding latch inside the vehicle until it fully extends to 40 mm (1.6 in). Take out the bcm by disconnecting its power extension cables at 40-way body wiring, the 32-way tan electric cable, and the 24-way gray electrical connector from the rear electrical center. Position slots on the bcm properly at the rear electrical center before installing the unit with downward pressure. Secure the bcm setup by hooking the 24-way gray, 32-way tan, and 40-way body wiring extension connectors to it. Press and hold the sliding latch until its locking tab inserts completely into position. Reinstall the rear electrical center cover next and put the left hand second seat back into its passenger position unless you are installing the chevrolet trailblazer ext or gmc envoy xl where you need to reinstall the left row seat. You need to complete the task and activate the new bcm setup when you replace it.

Start by closing the Ignition Switch before working with bcm connectors. Disconnect the 40-way body wiring extension then move to the 32-way tan connector and end with the 24-way gray electrical connector. Realign the 24-way gray connector first followed by the 32-way tan connector and finally attach the 40-way body wiring extension. The Body Control Module can find electrical issues even with the power off and protects battery power by maintaining light operation but does not locate electrical problems in parts it controls. Activate the power down now mode through the scan tool to find out any remaining power use on those circuits. Do not contact electrical contacts on the body wiring extension or try to open the bcm housing because both remain non-serviceable components that must be replaced as a whole unit. Start your work with the negative Battery Cable's removal. For chevrolet trailblazer ext and gmc envoy xl installations remove both second-row seats while chevrolet trailblazer, gmc envoy, and oldsmobile bravada owners should move the left second seat into cargo mode. You can take out the edgroom electrical box panel to find and release the bcm sliding retainer. Pull it toward you to 40mm until it hits its stop. We disconnect the three electrical connectors which include the 40-way body wiring extension, 32-way tan connector, and 24-way gray connector from the Body Control Module. Pull the bcm upwards out of the rear electrical center seat. Fit the bcm slots first to the rear electrical center then push it down to install. Plug in the 24-way gray electrical connector first followed by the 32-way tan electrical connector then the 40-way body wiring extension. Press the sliding latch to connect the bcm to the rear electrical center by moving it towards the center as the locking post locks into place. Reinstall the rear electrical cover and choose either passenger positioning for the left second seat (when needed) or put back the left second row seat for chevrolet trailblazer ext and gmc envoy xl models. Close the negative Battery Cable connection while programming any new bcm functions.

Make sure you turn off the Ignition Switch before detaching the negative battery terminal to upgrade the Body Control Module (BCM). Park the left hand second seat in cargo mode for chevrolet trailblazer, gmc envoy, or oldsmobile bravada models while the left second row seat needs to come off for chevrolet trailblazer ext or gmc envoy xl vehicles. Press the locking tab then press down and remove the bcm from the rear electrical center by sliding it toward the inner position until it reaches about 40mm (1.6in). Unplug the 40-way body wiring extension, 32-way tan electrical connector and 24-way gray electrical connector from the Body Control Module. Pull out the bcm from its rear electrical center trajectory. You should match the slots on the new bcm to the rear electrical center before placing it into position using a downward force. Link the 24-way gray electrical connector with 32-way tan electrical connector and 40-way body wiring extension to bcm entry points. Push the latch out toward the sides to lock the seating tab then place the rear electrical center cover back in place. For chevrolet trailblazer, gmc envoy and oldsmobile bravada install the left second seat placed to the passenger side while chevrolet trailblazer ext and gmc envoy xl drivers should install its left second seat. Stick on the negative battery connector and reset the bcm when replacing it.

First, remove the trim panel from the endgate.

Connect the negative battery cable and program the BCM if it is a replacement.

Remove the rear electrical center cover, press down on the locking tab, disengage the sliding latch, disconnect the connectors from the BCM, and then remove the BCM.

Use the scan tool to activate the POWER DOWN NOW mode.

Reconnect the electrical connectors as necessary, then reinstall the liftgate trim panel.