No Trailer Brakes and 2000 GMC Sierra Marker Lights Come On when the Brake Pedal is Pressed

Question

Question:

Hey guys, I have a 2000 GMC Sierra 1500 z71 with factory towing package, I use a Tekonsha prodigy P2 actuator and have a big tex 70ch tandem axle car trailer. When I plug the trailer in to the truck, actuator reads .c. Just like its supposed to, but when I get moving and push the brake in the truck nothing happens. However, when I hit the trolley brake manual override, as you guys call it the marker light in my pickup and the trailer come on and the brake works like it should only with the trolley lever, truck brake doesnt affect it also, I know the trailer is fine and the actuator is fine because they work perfectly in my fathers 01 Dakota. Same actuator and same trailer. Basically Im looking for somewhere to start searching on the pickup, any thoughts? Thanks!

asked by: Brian M

0

Expert Reply:

There are a couple of things that you can check to determine why the brake controller is only working with the manual override and not the brake pedal on your 2000 GMC Sierra. First, for the P2 # 90885, you should be using brake controller wiring harness # 3025-P.

It is possible though that the red wire is not in the correct location on the end that plugs into the truck. Make sure the truck end of the wiring harness looks like the picture I have included. If it does not then you can move the wires as needed or replace the harness. The truck marker lights coming on make me think the red wire is not in the correct location.

There are other tests you can perform as well. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle then there is something wrong with the controller and it will need to be replaced.

If it tests fine then reconnect the blue wire. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.

You can test the brake output pin and it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to track down.

If the truck side checks out fine then it could be the wiring to the brake magnets or the magnets themselves. Inspect the power wires to the magnets and look for pinched, frayed, or damaged wires and fix as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces.

You can visually inspect the magnets and if you can see the copper windings coming through the magnets will need to be replaced. To further test the magnets you can follow the help article I have linked. I have also included some help articles on testing and troubleshooting brake controllers for you.