Doors will lock but not unlock — What to check

Doors will lock but not unlock or vice versa

If you own one of the following vehicles and find that your Power door locks lock but won’t unlock (or vice versa) using the door lock switches, this may be the fix.

1997 – 1999 Chevrolet Venture 3.4L
1997 – 1999 Oldsmobile Silhouette 3.4L
1999 – 1999 Pontiac Montana 3.4L
1997 – 1998 Pontiac Trans Sport 3.4L

The door lock switches in these vehicles do NOT switch power to the door lock actuators. They are simply signal switches to the Body Control Module (BCM). The BCM provides power to the switches on the white wire for unlocking and the light blue wire for locking. When you flip the door switch, it connects the wire to ground. When the BCM sees power on each wire drop, it sends power to the door actuators. Unfortunately, GM placed a splices in the middle of each wire run. Both wires are spliced under the passenger door sill where water can seep in and corrode the splices (what were they thinking?). The splice can corrode, preventing power from reaching the door switches. Find the splices and look for corrosion. If you find it, clean the wires and re-splice. Cover the splice with heat shrinkable tubing to seal it.

© 2012 Rick Muscoplat