Its not too terribly hard to trace the wires... I am not a mechanic by any means, but I would think about tracing the wires out... you might find something the dealership would find out... you know? or you can disconnect each door lock and hit the button and find out which door it is (Make sure you wrap the other wires if you go this route)
2004 Ford Mustang GT Torch Red
Steeda: 2.25" stainless steel exhaust, UDP's, Dragon plenum, and CAI.