Dome Lamp
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 dome lamp is turned ON by the IP dimmer switch or during illuminated entry.
During illuminated entry or when the IP dimmer switch is ON the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, supplying voltage to all interior lamps. The BCM pulls the courtesy lamps low control circuit low, providing ground to the dome lamp and all courtesy lamps.