Anyone found and fixed this problem before? Trailer plug pin for running lights has low voltage. About 4 volts while pins for power, left and right turn signals have proper 12 v or 11.4v. Traced wiring harness to passenger side rear compartment and some of the wires go to F70 fused power source, ground on body and the rest go to a plug connected to some kind of box (not sure what it is). No fuse charts are found on any of the fuse boxes (engine, passenger side next to glove box, passenger side rear compartment).