Troubleshooting Tekonsha Prodigy P3 Brake Controller Only Works with Manual Override

Question:

The pickup it’s on is a 2005 GMC Sierra 2500 HD and I have the controller wired in with the wire harness fir that pickup

asked by: Mike

Expert Reply:

You have a problem with the red wire of the brake controller wiring of your P3 part # 90195 which is the circuit that tells the controller you are stopping the tow vehicle and to begin applying the trailer brakes. If you happen to have a late model GM truck this is most likely due to a blown third brake light fuse but otherwise it's probably the connection from the red wire of the controller to your truck's wiring.

I attached a help article on troubleshooting brake controllers for you to check out as well.

expert reply by: Jameson C

Mike

8/27/2021

The pickup it’s on is a 2005 GMC Sierra 2500 HD and I have the controller wired in with the wire harness fir that pickup

Jameson C.

8/27/2021

Most likely it is the third brake light fuse then. Check the fuse labelled CHMSL. A quick way to check this is to check to see if the third brake light works when you hit the brake pedal.