Troubleshooting A Factory Trailer Brake Controller That Is Not Activating Trailer Brakes

Question:

I have a 2010 GMC Sierra 2500 with factory brake controller, recently had brakes done.has 158k I also just purchased a 7X16 Pace cargo trailernew. With gain all the way up I get almost no braking from the trailer . Not really sure where to look first at the truck or trailer. The trailer dealer claims it was inspected by their shop when it came in and passed. Where would you look first? Also where does the signal come from to go to brake control? I also recently replaced the switch at the brake pedal. Any insight or suggestions would be greatly appreciated.

asked by: Ted

Helpful Expert Reply:

There are a couple of things you can test on your factory trailer brake controller on your 2010 GMC Sierra 2500.

The first thing I recommend testing is the vehicle and trailer connectors for corrosion. With this being an older vehicle there is a high possibility that there is some corrosion that has built up and is interfering with your trailer's brakes.

If you notice some corrosion, simply clean off the corrosion and check again for functionality.

The next thing you can do is check your ground wire on the vehicle and trailer connections, brake magnets, and trailer brake controller itself. If there is a loose or damaged ground connection, the trailer's brakes won't work either.

The last thing I recommend checking before delving deeper into troubleshooting is testing the functionality of your trailer brake controller with a circuit tester like the Circuit Tester Kit # PTW2993.

What you're going to need to do is, sever the brake output wire a few inches back from the controller, and apply the manual slide. You circuit tester # 40376 should be reading an output to your brakes.

Assuming this is a proportional brake controller, if the manual slide should activates the trailer brake output wire, you will need to try the brake pedal.

If the brake pedal activates the brake output properly, then the problem is farther back either in the vehicle wiring or on the trailer itself.