Circuit/System Description

WARNING: This page is about a different car, the 2006 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.

The CTSY/RF TRN fuse supplies battery voltage to the body control module (BCM). When the BCM commands the courtesy lamps ON, it applies battery voltage through the courtesy lamp relay control circuit to the coil side of the OVRHD LAMPS Relay, energizing the relay. Battery voltage from the inadvertent power courtesy lamp circuit is applied through the switch side of the relay and the courtesy lamp supply voltage circuit to the overhead console lamp, illuminating the courtesy lamp. The BCM also applies battery voltage through the courtesy lamp supply voltage circuit to the left and right roof rail courtesy lamps and the front, middle and rear door courtesy lamps. When any door is opened, the door open switch contacts close and the BCM receives a door-open input and it will illuminate the courtesy lamps. If the BCM receives a door lock or unlock input or a rear hatch open input, it will illuminate the courtesy lamps.