Circuit Description
WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) receives an ground from the courtesy lamp ground circuit. The sole purpose of this input is to provide a ground path for all of the courtesy lamps controlled through the courtesy lamp low control circuit.