How to Troubleshoot the Trailer Brake Controller

by Natalie Lyda

When a problem occurs with a trailer brake controller, it's possible to lose all braking power to the connected trailer's braking system. In order to avoid harsh stops or dangerous towing situations, it is imperative to troubleshoot trailer brake controllers as soon as they display any sign of malfunction. Depending on the specific brand and model of brake controller, troubleshooting procedures may vary slightly. However, the most common issues with trailer brake controllers are the same, regardless of brand.


Connect a trailer to the tow vehicle in order to engage the brake controller. Sit inside of the vehicle where the trailer brake controller is visible and easily accessible. Keep the brake controller owner's manual nearby as a reference guide.


Examine the position of the trailer brake controller. In order to function properly, proportional brake controllers require the in-cab controller unit to be mounted at a specific, level angle. Refer to the owner's manual to determine the suggested mounting angle for your controller and adjust the unit to meet the guidelines, if needed.


Look at the front of the trailer brake controller. Controllers with digital or LED display screens will commonly display a troubleshooting code in the event that the device is not working properly. Read and take note of any codes displayed on the controller screen. Reference the owner's manual for a complete list of your controller's troubleshooting codes and make adjustments to the braking system as recommended by the displayed code.


Check the wiring connection at the tow vehicle's positive and negative battery terminals if the brake controller displays signs of no power source. The positive terminal should have a firm connection to the black power wire coming from the brake controller, while the white wire should be securely connected to the negative battery terminal as a ground.


Check the continuity of voltage between the brake controller and trailer connector harness. Hold a 12-volt test light to the trailer connector wire port at the back of the trailer brake controller. After 12-volts of power have been confirmed at the controller, hold the test light to the wire connection port on the trailer connector at the rear of the vehicle. If there is less power at the trailer connector than at the controller, check for issues with the wiring between the two components.

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