The reverse lamp relay is controlled by the rear integration module, based on a bus input. With the proper scan tool, you could perform a function test of the modules capability to control the relay, and that would simplify the diagnosis. The cause could fall into a couple categories. A control problem, either by the vehicle not indicating reverse, the bus system not telling the RIM it is not in reverse, or the RIM not controlling the reverse relay. If you can manually verify that the reverse relay is activating, then you can move down the line. Another possibility is a broken wire at the rear compartment harness, at or near where it pivots when the lid is opened. Included here is a location of C400 which the signal and ground wire pass through.
(Domestic) (3 cavities) Body harness to the backup lamp harness, right rear corner of the rear compartment near the tail lamp
If there is power on the light green, and ground on the black(pins a and b respectively), you have verified that the relay is controlling and the problem lies between that connector and the backup lamps. Concidentally, are the license plate lamps also out?
Tuesday, February 22nd, 2011 AT 4:46 AM