The backup light switch is on the transaxle. If the backup lights don't activate with the ignition on and the shift lever in Reverse, check the ignition switch, GAUGE fuse, bulbs, and wire harness. If the lights remain on, inspect the harness. If one light works, examine its bulb and harness. To test the switch, remove the air filter housing and air inlet, disconnect the connector, and unscrew the switch. Use an ohmmeter to check for continuity when the plunger is depressed.