Chuck .. wrote:
2017 350 Ford daully....I step on the brakes the dash reads out and says that the left and right tailor lights not working/fault.
The right and left turn signal flashes rapidity when turned on. Also it says that the trailer is not connected.
#1 GROUND
Check all ground connections:
** truck 7-way
** Trailer umbilical
** Trailer brake leads
** Trailer lights
A bad ground connection explains the vast majority of trailer wiring problems.
#2 Trailer Brake wiring
Trailer manufacturers are notorious for cheap wiring of the brakes. Most often they daisy chain all the brakes together and run leads through the axle tubes. The daisy chain connections typically use scotch lock connectors which are great at corroding or not fully penetrating the wire insulation. Also the wires running though the axle tubes are famous for getting chaffed and causing a short to ground.
Usually when I've seen "Trailer Not Connected" it means there is a fault in the brake wiring connection. I've seen it twice in my RAM pulling 2 separate gooseneck trailers I had borrowed. One was really trashy wiring with corroded and broken connections. The other was because they had used non-standard wiring patterns in the trailer 7-way connector. Previously in my old truck I got NC (not connected) errors with my Prodigy brake controller. That issue was related to bad OEM brake wiring on the trailer.
KJ
