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 go on, then turn off the ignition switch. If the back-up lights don't illuminate, check 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, trace the leads back to the 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, there should be no continuity. 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 old switch, discard the old washer, install the new switch using a new washer, and plug in the connector.