Circuit Description
WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) controls the courtesy lamps through the courtesy lamp low control circuit. The BCM grounds the courtesy lamp low control circuit which completes the courtesy lamps ground circuit, and the courtesy lamps illuminate.