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 lamp supply voltage of the body control module (BCM) supplies battery positive voltage to the dome lamp, the liftgate lamp, and the map lamps. When any door is opened, the door jamb switch contacts close providing a door open input to the BCM. The BCM then provides a ground to the interior lamps with the switch in the AUTO position. The interior lamps receive a ground at G401 with the switch in the ON position.