This is our #1 customer topic. By popular demand, here is some more information about this error message. If you see this message, it means that the wiring between the brake controller and the trailer brakes may not be making a complete circuit or that the wiring connections are weak or corroded. The five most common causes for the Trailer Unplugged / Check Trailer Wiring error message are:

1. No trailer connected. The trailer must be connected with trailer brake wires connected properly.
2. Corrosion at the trailer plug on the bumper. Reseat connector, clean / replace if necessary.
3. Wrong wiring pinout. Make sure all wiring and adapters are the correct type and pinout.
4. A poor ground such as frame / ball ground. A dedicated ground return wire is recommended.
5. Broken / frayed wires or damaged electrical contact pins. Correct and repair as needed.

The MaxBrake brake controller is able to sense when the electric current loop is completed through the vehicle body wiring, the trailer connector plug, the trailer wiring, and the trailer brakes. If any part of this loop is broken, weak, or intermittent then the error message will alert the driver on the MaxBrake display screen. MaxBrake cannot tell you exactly where the problem is, but can alert you to potential problems that may limit your trailer brakes. If you see the Trailer Unplugged / Check Trailer Wiring error message, you may need a qualified electrician or service technician to troubleshoot and find the actual wiring problem in your vehicle or trailer. Even with this error message displayed, MaxBrake will still make every attempt to operate the trailer brakes, but no brake controller can operate a trailer brake system that is disconnected or inoperative. This means the current loop is complete, but it may be weak. Sometimes, other wires may be connected to the trailer brake wires by mistake. 99.9% of the time, the problem is not the MaxBrake brake controller. Try a different