Brake Controller Intermittently Reads 'Trailer Disconnected' After Brake Job

Updated 07/08/2021 | Published 07/07/2021

Question:

Hello I have a problem. Intermittently my truck will display a check trailer brake wiring or trailer brake disconnected message. I have replaced the receptacle on my truck and the 7 pin plug from the trailer. Funny thing is it never did this until I had a brake job done on the trailer. Could be coincidence I guess. Truck is 2018 ram 2500 and trailer is 2018 genesis toy hauler. Going to crawl underneath and check some wires and other stuff but I would appreciate any help or pointers I could get

asked by: Josh

Expert Reply:

A trailer brake controller sends a small amount of voltage back to the trailer brakes to check for resistance, to confirm that the trailer brakes are present and the trailer is connected. If something interrupts the connection between the brake contorller and the trailer brake magnets, you'll get a 'trailer disconnected' or 'check trailer brake wiring' message.

Start with the trailer connector on the vehicle, ensure it's not damaged or corroded which would prevent or reduce voltage from reaching the trailer brake magnets. You'll want to check the connector on the trailer for the same thing as well. If the trailer connectors check out okay, then trace the trailer brake output circuit from the trailer connector back to the trailer brakes. Look for loose connections or broken wires. Check the connections where the brake magnets attach to the brake output circuit. One lead from each magnet should have a secure connection to the trailer frame that is not corroded. The other brake magnet lead should attach to the brake output circuit. Make sure that connection is secure as well as the connection to the jumper running to the other brake assembly or assemblies.

Since you recently had brake work done, I'd guess that the connection at the brake magnets is your most likely issue. If you click the provided links, you can see some trailer braking and wiring troubleshooting articles that you might find helpful.

expert reply by: Mike L