Before testing the back-up light switch, check the fuse in the engine compartment fuse/relay box. Put the shift lever in Reverse and turn the ignition switch to the On position; the back-up lights should illuminate, then turn off the ignition switch. If the back-up lights do not activate, inspect the back-up light bulbs in the tail light assembly. If both the fuse and bulbs are functional, locate the back-up light switch on top of the transaxle, under the lifting hook, and for access, remove the air intake duct and the air filter housing and resonator. Next, remove the battery and the battery tray. Trace the leads back to the back-up light switch electrical connector, unplug it, and connect an ohmmeter or continuity tester across the terminals of the back-up light switch. With the shift lever in Reverse, continuity should be present; with the shifter in any other gear, continuity should not exist. If the switch fails this test, it needs to be replaced. If the switch is operational but the back-up lights are still not functioning, check for power to the switch. If voltage is absent, trace the circuit between the switch and the fuse block. If power is present, trace the circuit between the switch and the back-up lights for any open circuit condition. To replace the switch, unplug the electrical connector, unscrew the back-up light switch, and install the new switch using a new O-ring. Some models require RTV sealant to seal the switch; in such cases, clean the threaded hole of old sealant, apply new sealant to the new switch, and install it within five minutes of applying the RTV. Finally, plug in the connector.