Troubleshooting Trailer Brakes Not Working with 2009 Sierra 2500

Question:

I have a 2009 gmc sierra 2500 and 3 trailer 2 of the trailer are working fine but my 3rd one the breaks dont work but all light do and if i connect my trailer to an other truck every thing works

asked by: Stephane

Expert Reply:

Since you were unable to pinpoint the issue on the truck side or the trailer side by connecting them to different trailers/trucks, I recommend starting by using a circuit tester like # PTW2993 to test the 7-Way on your Sierra 2500. Make sure you have the brake controller in the truck adjusted to its highest setting and then apply the manual override. With the manual override applied, use the circuit tester to make sure you are receiving appropriate power at the brake output pin on the connector, which is at the 5 o'clock position.

If you aren't getting appropriate power there, then the issue is somewhere on the truck. Check the connector itself for any debris or corrosion that might be built up behind the pins, cleaning as needed. Make sure the wiring behind the connector is in good condition and you don't notice any damaged or frayed sections.

You may also want to test the brake controller itself to make sure it is working properly. To do this, you will just need to sever the blue brake output wire near the controller (leaving enough room to reconnect it) and then apply the manual slide. Using your circuit tester, you should get power to the controller side of the wire you severed. If you don't get power, test the wires going into the controller. The black wire entering the brake controller should have power and the red wire should only have power with the brake pedal pressed.

If you did get power at the Sierra's 7-Way with the manual slide activated, then the issue is somewhere on the trailer. Check the trailer side 7-Way for any corrosion or debris. Also check the brake assemblies themselves, specifically the ground wire coming from each unit. Make sure they are each connected to a clean, bare metal surface that is free of any debris. It's possible that a weak ground on one or more of the assemblies is just strong enough to provide intermittent function, which allowed everything to work fine on the other truck.

If you are still having issues, please let me know and I will be happy to look into this further.

expert reply by: Chris R