4 Pin Vs 5 Pin Trailer Wiring. Wiring your four-pin trailer can be a challenge when you first do it, but it's a simple do-it-yourself task. The left and right turn signal lights should each have a different color.
The first step in wiring your trailer cables is to ground the white cable first. I have hooked up a trailer light and it works manually, but I have not been able to get it to come on automatically. This accounts for three of the colors in the wiring harness.
Using this pin will only result in the device that you are powering being on even when the relay is OFF.
Cut the four-pin plug off of the trailer harness.
This accounts for three of the colors in the wiring harness. Any recommendations on where to get one? The first step in wiring your trailer cables is to ground the white cable first.