GM Service Manual Online
For 1990-2009 cars only

Power is supplied from the CTSY LP fuse in the IP fuse block through CKT 40 (ORN) at all times to the following components:

    • The LH and RH console courtesy lamps
    • The cargo lamp (utility)
    • The dome lamp
    • The inadvertent power relay in the body relay block

The inadvertent power relay is energized when the body control module (BCM) provides the ground to the relay coil through CKT 1393 (DK BLU). When the inadvertent power relay is energized, power is supplied to the coil of the courtesy lamp relay in the body relay block and to CKT 1732 (ORN). CKT 1732 (ORN) supplies power to the following components:

    • The IP compartment lamp switch
    • The underhood lamp switch
    • The LH and RH sunshade mirror lamp switches
    • The map lamps

CKT 1732 (ORN) provides a lamp request signal to the BCM. When the IP compartment lamp switch is activated, power is provided directly to the IP compartment lamp. The ground is provided by CKT 1050 (BLK) to G203. When the hood opens, the underhood lamp switch activates and provides power to the underhood lamp. The underhood lamp has a direct ground. When the sunshade mirror lamp switch is activated, power is provided directly to the sunshade mirror lamp. The ground is provided by CKT 1850 (BLK) to G202. The map lamps are provided ground when the map lamp switch is activated through CKT 1850 (BLK) to G202. The courtesy lamp relay is energized when the coil is provided power from the inadvertent power relay and the BCM provides the ground to the relay coil through CKT 690 (GRY/ BLK). When the courtesy lamp relay is energized, the relay will connect CKT 156 (WHT) to G200. This provides a ground through CKT 1850 (BLK) for the following components:

    • The dome lamp
    • The cargo lamp (utility)
    • The map lights (when map light switch is in the OFF position)
    • The LH and RH console courtesy lamps

For more information, refer to Body Control System Circuit Description in Body Control System.