Troubleshooting Output Shorted Error On Tekonsha P3 Brake Controller

Updated 04/21/2025 | Published 04/10/2025

Question:

This unit shows me output shorted, no brakes, but only when connected to a trailer. It does it for multiple trailers. What is the likely problem? Worked awesome for 6 months. Problem just started. 2003 Ford F150

asked by: Greg

Tekonsha P3 Output Shorted
(click to enlarge)

Expert Reply:

Hello Greg, thanks for reaching out. For the Tekonsha P3 # 90195 controller, the output shorted error is almost always due to a cut or exposed wire in the brake output circuit somewhere between the brake controller and the trailer brake assemblies. Since the same thing happens with multiple trailers, it sounds like the issue is on the vehicle side, or an issue with the controller. You could try disconnecting the blue wire from the back of the brake controller and see if the same thing happens. If the error goes away, we can narrow the issue down to the vehicle side. If the same thing happens this means your controller is bad and you should take advantage of the lifetime warranty.

Leave a reply below and let me know if there is anything else I can do to help.

expert reply by: Jesse M

Greg R.

4/21/2025

Hi Jesse, thanks for your reply. I have an update. I isolated it to the controller and tried a new one I purchased and it gave me the same error. Interestingly, I replaced the controller with a different brand and model and it works fine. Any insights? G

Jesse M.

4/21/2025

@GregR That is odd. My first though was it could be an internal short in the controller but that is super rare and would not explain why the same thing happened with the new controller. What other brand controller did you switch to?

Greg R.

4/21/2025

@JesseM It's a NAPA auto parts branded controller, the Agility. One final possibility is that the wiring harness I have for the Tekonsha is the faulty party. The new one I bought did not have the correct harness and so I used the old one. I have another coming this week to see if that was the problem. On a side note, I chose the Tekonsha because of its reviews, but from your perspective, does it offer enough of an advantage over the Napa Agility to keep troubleshooting or should I just keep what's working and call it good. Finally, how do I take advantage of the lifetime warranty? Thanks, G

Jesse M.

4/21/2025

@GregR Aha you know a bad wiring harness would explain it. I haven't heard of that happening before. It there anything visually wrong with it? Like a loose wire or something? I believe the NAPA agility is the same as the Hopkins Agility which is a pretty comparable proportional controller like Tekonsha. Tekonsha stuff is known for being good durable quality, and honestly I would probably not say the same about Hopkins products but if it works it works lol. The Tekonsha does offer a few more settings and display features. It would be nice to narrow down exactly what was wrong with the Tekonsha just to make sure we can avoid problems going forward. Do let me know what happens when you get around to testing the new Tekonsha harness.