Circuit/System Description

Battery voltage is applied at all times to the backup lamp PCB relay which is an internal part of the body fuse block. When the PRNDL is placed in the REVERSE position, a signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies battery voltage to the backup lamp relay control circuit energizing the relay. With the relay energized, battery voltage is applied through the switch side of the relay, the T/LAMP BCK/UP fuse, and the backup lamp supply voltage circuit to the left and right backup lamps. Or, the AUX/TRLR BCK/UP fuse and the supply voltage circuit to the backup alarm and the trailer connector. The engine may need to be running for the backup lamps to function.