Troubleshooting Curt 56421 7-Way Trailer Wiring Harness on 2019 Honda Passport

Question:

Purchased Curt Model #CU86FR 7 way connector kit for my 2019 Honda Passport Sport AWD. For a while I used a four pin and seven pin connected trailers with this kit and lights on trailer worked fine. Now however, the lights on both trailers stay on as soon as I plug them into this wiring harness kit. Even when the Passport is off. Lights on both trailers stay on permanently and blinking function does not work. Was using an Echo Bluetooth brake controller with it, but Im not sure it was properly working. Fuses all seem in good working condition and ground wire is on bare metal. My pic shows my tester with lights on as follows the vehicle completely shut off.

asked by: Jeremy W

Expert Reply:

According to my contact in the Tech Support department at Curt, a diode in the Curt 56421 harness which we sell as # CU86FR has shorted out which allows voltage to feed back into the trailer with the vehicle off. This is typically caused by a short circuit somewhere in the trailer wiring or by a dirty or corroded 7-way connector on the trailer. If the connector is showing green or white corrosion on the sockets, there's a good chance the corrosion has spread inside the connector which can cause adjacent circuits to contact each other.

You'll need to replace the # CU86FR, but before you plug the trailer in, you'll want to locate the short in the trailer wiring, or you'll damage the new harness. You'll want to trace each circuit from the trailer connector rearward, looking for loose connections and broken wires. Look for pinched wires or cracked or worn wire insulation. Once you locate the short and repair it, you'll be good to go. I'll link to a troubleshooting article that you might find helpful.

expert reply by: Mike L