Troubleshooting Tekonsha P3 Brake Controller Not Recognizing Trailer

Updated 05/20/2021 | Published 05/18/2021

Question:

Tekonsha p3 brake controller is not recognizing attached trailer. It did function at first tow. Now stuck at rv campsite. Repair service could not fix. Determined fuses all good. Some power at 7pin receiver when using manual override but none with brake pedal. Lights working. Suspect malfunctioning controller. The controller was recently purchased and installed with wiring via proper harness for vehicle - a Nissan Parhfinder . Both items purchased from etrailer. What can be done? Shoukd the controller be replaced?

asked by: Eileen D

Expert Reply:

For starters, the fact that you aren't getting output with the brake pedal doesn't indicate a problem. Proportional controllers like the Tekonsha P3 won't output voltage with the brake pedal unless the vehicle is in motion.

I'd begin by rebooting the controller. Unplug the controller at the rear, then plug it back in after a minute or two.

If the controller is reading 'NC' with the trailer plugged in, it typically means that the slight test voltage the controller sends out to sense if the trailer is connected isn't reaching the brake magnets for some reason. Usually, this is caused by a damaged/dirty/corroded trailer connector either on the vehicle or on the trailer itself. Check the socket on the vehicle and the plug on the trailer for damage. Check the pins/sockets for white or green corrosion. If you do see corrosion, there's a chance that it has spread to the interior of the plug and is preventing the signal from getting though. I'd also recommend tracing the brake output circuit rearward from the trailer connector to each brake assembly, making sure there's no loose connections or broken wires.

Worn brake magnets are also a less likely but still possible cause. If the face of the brake magnets are worn to the point where the interior copper wiring is visible, the magnets or brake assemblies will need replacement.

Another possibility

expert reply by: Mike L