Circuit/System Description

When the engine is running and the transmission is placed in reverse gear, the transmission control module sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the backup lamps. Once the driver moves the gear selector out of the reverse position, a message is sent by the transmission control module via serial data requesting the BCM to remove battery voltage from the backup lamp signal circuit. The BCM will not apply battery voltage to the backup lamps if the engine is not running.