How do you troubleshoot a trailer brake controller?
Check the wires on the trailer brake magnets. Each magnet should have two wires: one for power, and one for ground. Make sure that the ground wire is attached to a clean metal area without any paint or corrosion. The power wire should be intact and have a solid connection to the electric brake signal wire.
First, check the vehicle and trailer connectors for corrosion. … If there is a bad ground connection the trailer brakes will not work.