Hm. Well, the locks actually work. so maybe not BCM.
I'm now thinking it's the Remote Control Door Lock Receiver. According to my Gm Manual, this is located on the rear deck by the speakers - will have to remove deck cover to get to it. I wonder if maybe there's a wiring short of some kind to it, or the module itself is faulty. Ought to be able to see the wiring from the trunk. Seems that it's also the compass module.
Or... or I guess it's entirely possible that the locking has never worked for your fobs in the first place because they were somehow programmed wrong?
Might want to try reprogramming the fobs. Um... anyone have the instructions for this?
From my GM manual:
All transmitters which are to be recognized by the remote control door lock receiver (RCDLR) must be programmed in a single programming sequence. If the system is placed in program mode it will erase all previously programmed transmitters upon the receipt of the programming signal from the first transmitter. Up to 4 transmitters can be programmed. Do not operate or program the transmitters in the vicinity of other vehicles that are in the keyless entry program mode. This prevents the programming of the transmitters to the incorrect vehicle.
1. Install a scan tool.
2. Use the scan tool in order to access the Body Control Module (BCM) Special Function: Program Key Fobs.
3. Press the START soft key on the scan tool.
Important
The scan tool must stay connected until all of the transmitters are programmed.
4. Press and hold the LOCK button and the UNLOCK button simultaneously on one transmitter. After a delay of 5-10 seconds, the scan tool will indicate that the transmitter is programmed.
5. Repeat the previous step in order to program up to 4 transmitters.
6. Remove the scan tool.
7. Operate the transmitter functions in order to verify correct system operation.
