Trailer Lights Back Feed to 2008 Nissan Xterra with Unknown Wiring Harness Installed

Question:

I have a 2008 Nissan Xterra with an aftermarket Flat 4 trailer tow wiring set up installed at some random service station ... it has little indicator LEDs at the plug end that light up to show the proper thing eg tail lights. Here is the problem, when I attach my utility trailer plug in to the XTerra, wierd things happen to the XTerra electrical system, such as the radio light on the in dash OEM radio blinks on and off when the hazards are turned on ... the hazards on the trailer work ... then when I turn on a turn signal, the opposite side Xterra running light blinks as well ... Is this because an incorrect wiring harness was installed in the first place?

asked by: Gregory S

Expert Reply:

It is entirely possible that the wrong wiring harness was installed or a harness was incorrectly installed on your 2008 Nissan Xterra. There may also be a ground problem somewhere. If your Xterra did not come with a factory tow package then you would need to install harness # C56225 that you have referenced which comes with relays to activate the harness. On some vehicles, an additional relay is needed in the in-cab fuse panel. This relay can be obtained from the dealer.

It sounds like a 4-Way was hardwired into the tail light wiring on the vehicle but it was not done correctly so there are some strange back feeding issues occurring and possibly a weak ground on the vehicle side harness, trailer wiring, or both.

You will want to use the proper wiring harness and also make sure that all the ground connections on the trailer are attached to clean and corrosion free bare metal surfaces. I have included links to the installation instructions and a video showing a typical installation of the wiring harness for you.

expert reply by: Michael H