Troubleshooting Trailer Not Connected Error on Tekonsha Prodigy P3 Brake Controller

Updated 04/02/2025 | Published 04/02/2019

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Dielectric Grease for Electrical Connectors, 2 oz.

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Hook Probe Circuit Tester

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Question:

Trailer is not recognised by Tekonsha P3 Brake Controller I have a camper trailer which when hooked up to my Subaru Outback, using a Hayman Reese CompactIQ Brake Controlle, it is recognised and everything works fine but when I connect the trailer up to my Pajero using a Tekonsha P3, it says No Trailer. I know the Tekonsha P3 is working okay as it is fine when using on a bigger trailer both trailers have electric brakes but I dont know where to start troubleshooting. Is there any reason that my smaller trailer would not be picked up by the Tekonsha P3? Thanks

asked by: Luke

Expert Reply:

It is likely the 7-way pin connection on your Outback simply has a better connection to your trailer. The "No Trailer Connection" message when your trailer is physically connected means the controller is not seeing a power draw on the 5 o'clock position brake controller output pin. This about 95% of the time just means you need to clean your trailer connections using some sand paper and then use dielectric grease # 11755 to prevent moisture and debris from impacting that connection.

You can test this by using an incandescent circuit tester like # PTW2993 on each of the pins when you activate that pin function. The power draw for the light should cause that connection error to disappear and then the light should increase in intensity as you activate the manual override slide.

The other 5 percent of the time it is a bad ground connection or bad magnets on the trailer. I've attached a couple articles to assist with the troubleshooting.

expert reply by: Jason S

click to enlarge

Patrick L.

4/2/2025

If the pins are not the problem, then how do I go about checking the ground connection? I don't believe the brake magnets are the problem as the trailer works fine on other vehicles. Thanks for your help. Pat

Jameson C.

4/2/2025

@PatrickL Is your problem exactly like what is described in the first question?

Patrick L.

4/2/2025

@JamesonC Yes.

Jameson C.

4/2/2025

@PatrickL To check the grounds is basically first check to see where the ground wire on your trailer 7-way goes to. It will either run directly to the trailer frame or to the assemblies directly. If you have an aluminum frame it will be very important that the assemblies ground directly to that main harness.