Message center displaying "Wiring Fault On Trailer":
This may occur due to water intrusion/corrosion in the trailer connector socket or the connector behind the socket. If corrosion is present, replace the socket and harness and lube with silicone dielectric grease. If there are no signs of water, perform normal diagnosis. Broadcast Message 7052, 7108.
I have seen some of the connectors with very little dielectric grease in them. Pull the connector off and clean everything good, then fill the bastard with dielectric.