Troubleshooting a Plug in Wiring Harness for a 2024 Ford Bronco Sport

Updated 02/20/2025 | Published 02/15/2025

Question:

All trailer lights work correctly until I crank the truck then brake and turn signals quit but running lights stay on. Could that be a bad ground on the truck? 2024 bronco sport big bend with plug and play wiring system.

asked by: Stanley B

Expert Reply:

That sounds about right Stanley. It's either a bad ground or a bad control module. Both harnesses we have for your Bronco Sport item # TK46FR and item # C47WR require you to ground the harness out to a bare clean piece of metal with no paint or corrosion. I recommend checking to see if it's come lose or is dirty.

expert reply by: Jerred H

Stanley B.

2/19/2025

I have tried checking the ground and even ran a ground wire from the battery . Have purchased another curt wiring harness still does the same thing. The tail lights on the bronco ar incandescent and the trailer lights are led will that have anything to do with it. I am at my wits end.

Jerred H.

2/20/2025

@StanleyB Yeah that's your problem then. You can try to hook up to another trailer to confirm or use a tester like item # I26 but the LED lights on your trailer are responding incorrectly because of the incandescents on your Bronco. You'll want to wire in the Load Resistor Kit for LED Turn Signals item # DI34ZR to your trailer lights.