Wiring problem for 2005 Pathfinder trailer hitch harness. Brake lights work on left side, no running light or turn signal. Right side turn signal and brake lights work. Replaced harness, but result is the same. Tested trailer wiring with another vehicle, all systems fuction. Should I by-pass the harness and wire tow vehicle side thru taillights.

Does your Expedition have a receiver/trailer hitch and wiring harness? If so, is it OEM (factory) or aftermarket? I suspect that your trailer wiring harness has one or more wires that have chafed insulation and the conductors inside the wires are rubbing together. If the wiring is OK, look at the Trailer Tow relay as a possible culprit.

I have the same problem.

you must check the connection where the truck harness meets the added trailer harness on the truck itself not the trailer harness.

One wire is for the brake/directional filament and the other wire is for the tail light. The fixture should be grounded when it is attached to the bracket. To test which is which (the brown wire is USUALLY the ail light) make sure the fixture is grounded and touch a hot wire to each of the wires coming from the fixture. Watch to see which wire lights up the brighter filament and this is the brake/directional light. The dimmer filament if the tail light. Brakes lights and directional lights are both the same filament. Wen the brakes are applied, both lights are activated. When a direction light is turned on, it simply flashes the brake light filament.

seperate fuse box under hood some time, alldatta is in your library

Hello. Actually the color code for trailer hitches is universal.

• White - Ground
• Brown - Running (tail) lights
• Yellow - Left turn/brake light
• Green - Right turn/brake light

Regards, Joe
PS please rate my answer.

First check the fuses. There may be one for trailer running lights. Check also power at the harness. If the brake lights and turn signals are seperate, there has to be a converter from 5 to 4 wire. For the power to feed back to the brake lights it sounds like the vehicle wiring is direct and not using a converter... or one of the bulbs on the trailer is contacting both contacts. Try http://www.etrailer.com/faq-wiring.aspx and maybe get a simple 4 pin tester that plugs into the 4 pin connecter. Hope this helps.

for your trailer you need park light, brake light, left and right signal light. the best way is to tap them in the rear tail light wires.

You have a bad ground wire. It will be eithr the ground on the trailer or the car harness. To confirm this diagnosis, take a set of jumper cables and hook one end to the trailer tongue and the other end to the car hitch. If your lights work, then you know it is a ground. The other possibilty is that you have a blown fuse.

White - Ground
Brown - Running Lights
Yellow - Left Turn, plus Stop
Green - Right Turn, plus Stop

Hope this helps!