GM Service Manual Online
For 1990-2009 cars only

The remote control door lock receiver is supplied voltage at all times from the TBC fuse on CKT 1140 (ORN). Ground is supplied on CKT 1850 (BLK) to G203.

When a button the transmitter, (key fob), is depressed, the receiver sends a wake up signal to the body control module (BCM) on CKT 416. Along with the wake up message, the receiver sends the command to unlock, lock or panic mode to the BCM. If there is no DTC associated with the requested command, the BCM will lock, unlock the doors or place the vehicle in panic mode, flash the exterior lights and sound the horn.

The BCM supplies a small voltage on CKT 416 called a bias voltage which enables messages to travel from the remote control door lock receiver to the BCM. The BCM also sends messages to the remote control door lock receiver i.e. program mode.