No Running Light Signal and 4-Flat Connector on a 1999 Ford Expedition

Question:

Hi, Hoping you can help me out.... I have no signal reading that goes to brown wire tail lights at vehicle side receptacle. I have right and left turn signals and break lights but no running lights, I have white wire grounded to trailer very well. Is there a fuse or something on the 1999 expedition that controls the trailer hook-up connector for running light signal? I metered at the recept that came on the truck bumper and there is no signal coming from truck side. I looked at fuse panel diagram and just didnt see a running light fuse callout, is it under another fuse function? Any suggestions...? Thanks

asked by: Ron P

Expert Reply:

To determine why you do not have a tail light signal at your 4-way trailer connector, you will want to check a few things. If you have a factory installed 4-way connector on your 1999 Ford Expedition, then you will want to check fuse number 5 and relay number 201. This is the fuse and the relay that control the running light function on your trailer wiring harness.

If you replace the fuse and relay and still have the problem or if you have an aftermarket wiring harness installed, then I would recommend taking a look at the wiring harness itself. The first indication of any issue would be corrosion on any of the pins. If there is corrosion, then I would recommend cutting off the original 4-way connector and replacing it with the 4-Pole Hardwire Kit, # 18252.

If you do not find any corrosion or damage, then you will want to follow the taillight wire and use a circuit tester, like part # PTW2993, to probe different points until you find where the signal terminates. You may discover a pinched, frayed or damaged section or bad connection causing your issue.

I have attached a video of our technician using a circuit tester to test wires for signal for you to check out.

If you are unable to resolve your issue or find the problem after following these steps, then let me know what you find, and we can take further troubleshooting steps.

expert reply by: John H