Circuit/System Description
WARNING: This page is about a different car, the 2007 Suzuki XL7. However, it is still accessible from the selected car via links, so may be relevant.
The courtesy lamps are controlled by the body control module (BCM). Inputs from the dome lamp switch and the door ajar switches are monitored by the BCM. When a door ajar switch is closed the BCM supplies the ground for the courtesy lamps or the dome lamp switch is turned to the ON position. The BCM also supplies the voltage for the courtesy lamps.