Troubleshooting Tekonsha P3 Brake Controller 90195 Overload Issue

Question:

I have an issue with my P3 Tekonsha. We went to pick up our new trailer. We got everything all connected and started driving away, however, immediately, I received Overload - No Brakes. Even though it did say, the brakes still worked but did more of a pumping action. To troubleshoot, we hooked up a different model Tekonsha fresh from the box. The same overload issue happened. The dealership where we bought the trailer hooked it up to on of their vehicles with the same P3, and no issue. I took my vehicle, a 2016 Pathfinder to a Hitch Shop where they hooked up voltage meters the 7 pin and tested it. The tech told me there is NO issue with our vehicle. What should our next steps be? Also, i leared more about the P3 and only understand the troubleshooting now. When i brake without a trailer, i am getting full voltage output however, output current is 0.0. Is this normal? Thanks.

asked by: Bryan S

Expert Reply:

Since your local technician tested your Pathfinder's 7-way and found it to have a functional trailer brake circuit, AND since your new trailer behaved properly when connected to another tow vehicle, the issue I suspect you might have is an intermittent short in the trailer wiring.

If the trailer is not brand new there could be corrosive build-up on or even inside the 7-way plug. Water can over time migrate into even a sealed/molded 7-way plug like # H20046 and cause adjacent circuits to become bridged together. Sometimes the action of inserting the plug into the tow vehicle socket can make such a condition appear or disappear spontaneously. You can test the trailer brake circuit directly, when it is NOT connected to the Nissan, by using a set of jumper cables and two lengths of wire to directly connect your Pathfinder battery (or another that is well-charged) to the ground and brake circuit pins on the trailer 7-way plug. Please see the linked photo.
With this direct 12V power application the brakes magnets should audibly hum and you should feel the brakes engaged as you try to rotate a wheel.

The other possibility is that your 7-way socket on the Pathfinder is not configured correctly to match the trailer's wiring. 7-way wiring can be set up in more than one way, despite there being a common convention as shown in the linked article. If you have a circuit tester like # PTW2992 you can yourself test the 7-way's various circuits to confirm both proper configuration and operation of each of those. Please refer to the linked video for a demonstration of using a tester.

Last, make sure that on the P3 main setup menu screen you have selected the correct operating mode to match the type of brakes on your trailer. If the unit were set to function with EOH (electric over hydraulic) brakes rather than standard electric drum brakes this could generate a fault code.

With no trailer connected the unit cannot deliver current to the brakes so that reading is normal.

expert reply by: Adam R