Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Ion Red Line, 2007 Saturn Ion 3, and 2007 Saturn Ion 2. However, it is still accessible from the selected car via links, so may be relevant.
When the headlamp switch is turned to the HEADLAMPS or Parking Lamps position, the body control (BCM) applies battery positive voltage to the instrument panel (I/P) courtesy lamps. When a door is opened, the door latch assembly applies a ground to the BCM. The BCM supplies battery positive voltage to the courtesy lamp supply voltage circuit and applies a ground to the courtesy lamps low control circuit.