Troubleshooting Trailer Braking System With Brake Controller Indicating OL or Overload Error Code

Published 01/16/2016

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Question:

2005 Chevy Colorado, everything wired in as best I could. I got infrequent overloadfoot messages on my controller, the TK90160. It happens when the trailer is loaded and unloaded. Just what does the overload mean? With an empty trailer, Im WELL under the 4000lb rating.

asked by: Robert S

Expert Reply:

The OL or overload error code indicates a short in the brake output circuit. As a first step, you will want to see if the problem exists with the wiring on the trailer or on the vehicle. Due to its intermittent nature, I'm suspecting a loose connection or a worn wire in the brake controller's output circuit.

Try unplugging the trailer and activating the manual brake switch on the controller. If you get the error code at that point, it is a pretty good indication that the problem exists on the output circuit between the brake controller and the trailer connector. First, check the connector itself. Make sure it is not damaged or corroded. If you can see white or green corrosion on the trailer connector's pins, there is a good possibility that the corrosion has migrated to the interior of the connector. If you can access the rear of the connector where the wires attach to the terminals, check those for corrosion and repair or replace if necessary.

If all appears well with the trailer connector, sever the blue wire a few inches behind the controller (leaving enough room to reconnect it later). Try the manual switch again. If the error code has disappeared, then the short is in the wire between the controller and the trailer connector. Simply run a new length of # 10-1-1 from the controller to the trailer connector, bypassing the wire that has the short.

If the OL code only occurs when the trailer is connected, then the problem lies with the wiring on the trailer. Check the trailer connector for damage or corrosion. Trace the brake output circuit (usually a blue wire) from the trailer connector back to the brake assemblies looking for broken or pinched wires or loose connections. Examine the wire insulation, looking for worn or cracked spots that would allow the copper conductor to contact the trailer frame or other metal. Make sure that one lead from each magnet ties into the brake output wire, and the other grounds to the trailer frame. If all this checks out OK, your magnets might be worn. Pull off one of your hubs, and examine the face of the magnet that rides against the inside of the brake drum. If you can see any of the interior copper wiring encased in the magnet, the magnet is worn to the point of being unserviceable and should be replaced.

I have linked you to a brake magnet and brake controller troubleshooting FAQ article that you might find helpful.

expert reply by: Mike L