When towing my fifth wheel trailer I get a message “check trailer wiring” immediately followed by “trailer connected”
This happens at random and is driving me insane.
Dealers checked out wiring on truck and trailer and both reported no problem.
Towed for 2 years with no problem but now it’* happening all the time. Anyone experiencing this problem?

Intermittent problem. I would wiggle the harness and bang around each light and see if you can find the problem area.

What carfixer007 said ^^^^^^^

. . . and maybe try securely connecting a ground wire between the trailer and tow vehicle and see if the problem goes away.