Tail running and license plate lights out but turn signals and brake lights work. No fuse is blown.

I’m in a predicament. Recently my tail running lights have gone out. My signals and brake lights still work. I’ve checked each fuse and they are all fine. The bulbs are all new. I’m thinking there is some wiring issue or water damage.

If one connector gets damaged does that short out the rest of the line, wouldn’t a fuse be blown though?

Anyone else have this issue where the fuses looked fine? Where did you find and solve the issue?

 

Do you have aftermarket trailer light wiring? I had issues on my first gen with the internals of the aftermarket trailer t-connector melting and giving me all kinds of issues with turn signals, lights, etc.

 

I used to but tried taking all unnecessary wires out. I may have missed some though. Where would something like that connect to at the source?

 

On my truck it was connected at the tail lights, those wires ran to a little control box that you secured under the truck, then the 4 pole flat plug ran to the hitch. My issue was the connections in the little control box failed. The easiest way to troubleshoot was to unplug the trailer wiring harness from the tail light and see if it fixed the issue. In my case it did.

factory trailer wiring is not as simple I believe as it would be running up to the dash and be tied into the flasher, fuse & relay box, etc.

 

Okay so I pulled this out of the interior fuse box. Definitely doesn’t look OEM and was connected to a wire that went nowhere. Nothing changed after removing it. I’m trying to remove every and all trailer wiring because I’m not going ever going to tow anything. When installing trailer harnesses do you splice wires with the tail lights? Wondering if there’s some faulty wiring because of that.

 

Doesn’t look like an OEM relay and while no way to know for sure what it’s from, probably some kind of aftermarket light or something.

When I’ve installed trailer light wiring (non-oem) it’s been plug and play except for running a ground wire. I’ve never had to splice into a harness, that doesn’t mean someone didn’t.