Troubleshooting Trailer Brakes that Lock Up When Headlights are Turned On

Question:

Hello, I have a 2015 Toyota 4Runner and prodigy P2 brake controller. I used the Toyota factory wiring harness and double checked the wiring diagram. Problem I have is that when I turn on the vehicle lights the prodigy engages the trailer brakes simultaneously and the ABS lights come on. When I turn off the lights the problem goes away. Is ther a work around or should I send back my prodigy and get another brake controller. Also I was just informed that while the prodigy is still plugged in but am not towing anything the dashboard lights dim when the brakes are pushed. Please reply soon, as I need to get this fixed ASAP before I leave town again. Thank you for your time.

asked by: Neil S

Expert Reply:

There's a short between your running light circuit and your brake output circuit. That's why when you turn the headlights on the brakes are locking up.

That explains the weird dash light issue as well. Most likely the issue is the rear trailer connector and is a short between two circuits. Check there looking for any corrosion/cut or exposed wire and fix as needed.

expert reply by: Jameson C