There's no reference to a backup light relay in the service manual, but they do show three relays that are not used. They are the first one in the corner of the PDC, the sixth one in line, and the eighth one at the end of the row.
First, check fuse #4, a 15 amp in the junction block inside the car. If it is good, use a test light or voltmeter to check at the tail lamp housing. The backup lamp circuit is the violet wire with a black stripe. It should have 12 volts with the ignition switch in the "run" position and the transmission in "reverse".
If the 12 volts is missing, check for 12 volts at fuse #4. If you have voltage there, suspect a defective transmission range sensor.
If you do have 12 volts at the tail lamp housing, inspect the plastic ribbon cable for burned spots, particularly where the copper circuits go around a sharp corner or become very skinny. If there is a burned spot, replace the circuit or housing.
Monday, January 25th, 2010 AT 7:42 AM