Okay, so the power lock mechanism works but not the door switches. It looks like the switches only share two items. The ground connection and the body control module itself. To check which is the issue we can test right at either switch. Let's use the passenger side as it gives us a bit more room without the steering wheel in the way. Use a trim tool with a wide flat blade (butter knife or similar will work) and look at the trim piece that the door lock button is in. Use the trim tool to slip under the front edge of the trim and find the release tab for the trim piece. Release it and the trim should rotate out of the door panel. There will be a connector on the switch with a few wires in it. The ones you are looking for are the white and black ones. To test if it is the module we need a grounded piece of wire. Unplug the connector and touch the piece of wire to the terminal that goes to the white wire, with the key on. If the door locks trigger when grounded the issue is most likely the ground connection. If they do nothing it could be the body module. To test that plug the connector back into the switch. Now look at the spot where the black wire comes out of the connector. Use a pin to back probe that connection. You want to use the needle to push into the connector and then connect the grounded wire to the pin. Now try the switch. Do the locks now work? If yes, then go find the ground connections contact point at G301 which is behind the rear seat back and repair it. Or run a bypass ground by finding the black wire where it comes out of the door harness at the A pillar and adding a ground there. If the initial testing shows that the BCM is faulty and not the ground connection, then you will need to replace it. However, to replace it you will need a factory level scan tool and access to GMs programming software. Then you need to pull the build data from the existing BCM and load that into the replacement.
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Apr 4, 2024 at 9:09 AM
