Troubleshooting Trailer Brake Controller that Shows Trailer Disconnected Message

Updated 08/26/2016 | Published 08/25/2016

Question:

its a 2012 ford f-350, the truck is showing that the trailer is disconnected when plugged into the trailer?

asked by: Chad K

Expert Reply:

The most common cause for a trailer brake controller to display the 'no trailer connected' error message is a damaged or corroded connector either on the vehicle or on the trailer. Corrosion can occur inside a connector too so you'll want to inspect both the external contacts and the back/inside of the connectors if possible for signs of any corrosion. Also check any wiring that plugs into the back of the vehicle socket.

Even slight greenish or whitish discoloration can indicate a corrosion issue, and certainly it can also happen that there can be severe corrosive build-up inside the connectors. If you have a spray-on electrical contact cleaner like Caig De-Oxit you can try applying this to remove the corrosion.

Other common causes for this error message are a bad connection at the electric brake assemblies or a short on one of the magnets. There could also be damage or a short on the wire that carries the brake circuit. Check both the truck and trailer.

You can test the trailer easily simple by disconnecting it from the truck and applying 12V power directly to the brake circuit contact. On a trailer plug this will be the pin indicated by the arrow shown in the linked photo. If your brakes engage when you give them direct power, then the problem is likely to be on the truck wide.

A troubleshooting article is linked for you.

expert reply by: Adam R