Windshield Header & Roof Rail Courtesy/Reading Lamps

Voltage is applied through INT LAMP Fuse at all times to the Body Control Module (BCM) which in turn applies voltage to the Courtesy/Reading Lamps.
^ For the reading function, the Courtesy/Reading Lamps will illuminate whenever a door is opened or whenever the I/P Dimmer Switch is turned to DOME. Ground for this circuit is supplied by the BCM CKT 690 whenever it senses a ground in CKT 149 (LH Front Door) or CKT 49 (RH Front, LH and RH Rear Doors) from the Door Ajar Switches or B+ from the I/P Dimmer Switch. A timer in the BCM will extinguish the Courtesy Lamps after approximately 10 minutes if the I/P Dimmer Switch was left ON or the doors were left open with the Ignition OFF.
^ For the reading function, when turned ON, these switches close to ground through CKT 350 allowing for individual operation of these lamps.