Courtesy Lamps

WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

When either one of the front doors is opened, ground is applied through the door latch door open switch and the door open switch signal circuit to the door module indicating the door open position. In response to this signal, the door module sends a GMLAN serial data message to the BCM of the door open position. Or, when either one of the rear doors is opened, ground is applied through the rear door latch door open switch and the rear door open switch signal circuit to the BCM indicating the door open position. Once a door open message or signal is received, the BCM will then apply battery voltage from the CTSY/RF TRN fuse through the courtesy lamp supply voltage circuit illuminating the lamps listed below. At the same time the BCM sends a GMLAN serial data message to the driver door module (DDM) and the front passenger door module (FPDM) indicating the courtesy lamps ON request. In response to this message, the door modules apply battery voltage to the courtesy lamp supply voltage circuits illuminating the front door courtesy lamps. The front door modules also provide a ground through the low reference circuits to the courtesy lamps.

Courtesy lamp module (w/o V4U or BQ9)
Rear door courtesy lamps
Overhead console lamp (w/ V4U or BQ9)
Roof rail courtesy/reading lamps (w/ V4U or BQ9)
Dome lamp (w/ V4U or BQ9)
Middle door courtesy lamps (w/ V4U)