I guess this one could fall under the electrical section or this one. I'll start off by saying we've ruled out this being a problem with the trailer wiring because ...

I guess this one could fall under the electrical section or this one. I'll start off by saying we've ruled out this being a problem with the trailer wiring because we've checked the lights with other trucks and they work fine. Heres the problem…

The running lights (ya know, the 50% dimmed tail lights at night? I think they're called running lights) do not work with any trailer with my truck. Blinkers and brake lights do. Anyone have the answer? Is it a fuse?

Also, its not a corrosion/rust/connection problem. Ruled that out and cleaned the connections anyway

There are trailer fuses under the hood. Check em.

On my trucks the trailer light fuses are inside the truck in the fuse panel, which is on the driver side of the dash only accessible when the door is open. I`ve had these trailer light fuses blow before. But my trucks are both 04`s the NNBS may be different.

You did run the wires bundled up underneath the hood to where they belong I assume? And install the appropriate fuses?

Well replacing the "parking lamp" fuse (it was the number 25 fuse under the hood) fixed my truck. Now my dad's suburban is having the same issue…all lights but the running lights work. And it's not a fuse, or the connections. I guess it has to be a wiring issue

Glad you figured your problem out.