Marker lights don't work, turn signals do?

You ever figure this out? I’m having the same issue this morning. Parking lights will not come on after keeping them on overnight lol. Same truck

 

I just fixed this one. After you've checked the fuses and swapped a couple of relays. Disconnect the Trailer Wire harness to isolate the tractor. Flip on the running lights if you have the same problem it's in the tractor. If you don't it's in the trailer. Visually inspect for damaged wire loom or exposed wires. Separate wires that look rough just to make sure they're not touching then check again. Follow it up with some wire tape as a field repair. I like to use liquid tape in a can. Your mother told me to tell you hello...