I/P Courtesy Lamp
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The I/P courtesy lamp is turned ON by the IP dimmer switch or during illuminated entry.
During illuminated entry or when the I/P dimmer switch is DOME the BCM wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps.