Backup Lamps

The backup (or reverse) lamps have a path to ground at all times through a takeout and eyelet terminal of the body wire harness that is secured to the body sheet metal within the passenger compartment. On vehicles with a manual transmission, the backup lamp switch provides an input to the BCM through a backup lamp switch signal circuit, and the BCM provides battery voltage to the backup lamps on the backup lamp control output circuit whenever the ignition switch is in the ON position and the REVERSE position is selected with the transmission shift linkage.

On vehicles with an automatic transmission, the PCM continually monitors a hard wired multiplex input from the Transmission Range Sensor (TRS), then sends the appropriate electronic transmission gear selector status  messages to other electronic modules over the CAN data bus. Whenever the ignition switch is in the ON position and the BCM receives an electronic message indicating the status of the transmission gear selector is REVERSE, it provides a battery voltage output to the backup lamps on the backup lamp control output circuit.