The back-up light circuit is controlled by a plunger-type switch located on the left-hand side of the Getrag transmission casing and the right-hand side of the ZF transmission casing. If a fault occurs, first check that the circuit fuse is intact. To test the switch, disconnect the wiring connector and use a multimeter set to the resistance function or a battery-and-bulb test circuit to verify continuity between the switch terminals only when reverse gear is engaged. If continuity is not present and there are no visible breaks or damage to the wires, the switch is faulty and needs replacement. To remove the switch, raise the vehicle and support it securely on jackstands, then disconnect the wiring connector and unscrew the switch from the transmission casing. For installation, screw the switch back into the transmission housing and tighten it securely, reconnect the wiring connector, and test the circuit's operation before lowering the vehicle to the ground.