Circuit/System Description

When the transmission is placed in reverse gear, the engine control module (ECM) 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. The reversing lights are permanently grounded. When the driver moves the selector lever from the reverse position, ECM sends a message to BCM via serial data to cut off battery voltage from the reversing light control circuit.