Auto Door Locks Will Not Lock - keywords ajar automatic inop message no open power

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

The customer may comment the doors do not automatically lock when the vehicle is shifted out of park, or at 5 MPH depending upon how their personalization is set. The doors will continue to lock normally using the power door lock switches and keyless entry transmitters.

The BCM must see all the doors are closed. Each door has two separate switch signals, the OPEN and the AJAR signals. Both are located in the door latch assembly. The front door switch signals are monitored by Driver Door Module (DDM) or the Passenger Door Module (PDM). The open and ajar status is reported to the BCM via Low Speed GMLAN. The rear door OPEN and AJAR switches are monitored directly by the BCM. The door OPEN switches are electrically "open" with the doors closed, and "closed" with the doors open. The door AJAR switches are not used for auto door lock function.

Monitor the front door OPEN switches using the Tech2, under Driver or Passenger Door Data. The Tech 2 will display Active with the doors open and Inactive with the doors closed. Open and close the doors to ensure they change states appropriately. At present, the Tech 2 does not display the status of the rear door OPEN switches. The left rear and right rear door open switch circuits (ckt 1179) are wired in parallel through S343 to BCM C6 (pink) pin 16. With both rear doors closed, check for a short to ground at pin 16. If continuity to ground is present, one of the rear door switches are likely stuck closed. Disconnect the electrical connector from each rear door latch assembly one at a time. Replace the latch assembly that causes the short to stop when disconnected. If continuity to ground at pin 16 remains with both latches unplugged, ckt 1179 wiring is shorted to ground in the door or body harnesses. Inspect and repair the harnesses as necessary.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.