"Wiring fault on trailer" message - Ford Truck Enthusiasts Jun 17, 2007wiring fault on trailer message comes on with trailer hooked up. But everything works fine. The higher I have the gain turned up the more the message pops up. Then theres other times if I use the trailer brakes alot under heavy load, The trailer brake controller will turn off and will read trailer disconected. Thus no trailer brakes."trailer wiring fault" code on dashAug 11, 2012" Wiring Fault On Trailer " or " Trailer Disconnected " onMar 18, 2011See more results Trailer wiring fault displayed. Didn't know where to start Jun 08, 2017Trailer wiring fault displayed. Didn't know where to start. 2015 f150 lariat. Originally sold in Canada. Bought last July from iowa ford dealer Mechanic's Assistant: Are you fixing your F150 yourself? What have you tried so far? Not fixing myself. Warning showed on dash couple weeks ago. Battery went dead two days ago.