Troubleshooting A P3 Brake Controller That Shows no Trailer Connection

Question:

Tekonsha P3 installed 2 years ago on a 2002 GMC Sierra 2500 HD with the tow package.I am receiving a No trailer connected message. Trailer is 2 year old enclosed aluminum snow trailer. Checked Ohms on the trailer brake circuit of the trailer showing 5 ohms. Checked brake output voltage of P3 at the rear of the truck with the truck on and manual slide activated and had no voltage. Trailer lights, turn signals and brake lights work fine. Bad controller?

asked by: Jim P

Expert Reply:

You've eliminated the trailer as the problem, so that leaves the truck side of the equation. The easiest way to test to see if the problem is the controller is to cut the blue wire leaving the controller leaving enough room for it to be reconnected and then test the exposed wire coming out of the controller with the manual override lever. If there is voltage there then you know the problem lies in the wiring between the controller and the 7-way. I would recommend checking the fuses under the hood of your truck at this point.

If there's no voltage there when the lever applied then you know the controller is bad an needs to be replaced.

I attached an FAQ on troubleshooting brake controllers for you to check out also.

expert reply by: Jameson C