Interior, Courtesy Lamps Circuit Description

The MIRROR (Pontiac) or RDO/INT (Chevrolet) fuse in the IP junction block supplies battery positive voltage to the Body Control Module (BCM). The inadvertent power control circuit of the BCM supplies battery positive voltage to the IP junction block. The IP junction block supplies battery positive voltage to the left and right hand courtesy lamps and the dome lamp. When any door is opened, the door jam switch contacts close and the door open input to the BCM is grounded. The BCM provides a pulse width modulated ground to the left and right hand courtesy lamps and the dome lamp for the theater dimming feature.

The IP junction block also supplies battery positive voltage to each reading lamp and the rear compartment (trunk) lamp. When their switches are closed to provide ground, the lamps will illuminate. The dome lamp switch has three positions, DOOR, OFF and ON. When in the DOOR position, the dome lamp operation is controlled by the BCM. The ON position provides a ground for continuous operation. The OFF position turns off any dome lamp operation. If the driver inadvertently leaves any interior lamp on, the BCM will turn it off in 18-22 minutes.