Battery positive voltage (B+) is applied at all times through the underhood fuse/relay center PARK/REV Fuse to both the switch and the coil of the reverse relay in the rear compartment relay center 5. When the gear selector is placed in the REVERSE position, the body control module (PZM) receives a Class 2 message from the powertrain control module (PCM) indicating that the vehicle is in the reverse gear. The PZM then grounds the reverse relay coil, energizing the relay. The relay switch contacts close and battery positive voltage (B+) is applied to the backup lamps. The backup lamps are permanently grounded at G402, and will remain lit until the gear selector is moved out of the reverse position and the PZM will removes the ground from the reverse relay. The relay switch opens, removing the battery positive voltage (B+) from the backup lamps. The PZM will also turn off the backup lamps if the ignition switch is turned to the OFF position.