Running lights do not work?

It sounds more like a hazard switch that is out. Here is the wiring diagram and a guide to help you do some testing so you can get the problem fixed.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Here are the blinker light wiring diagrams and you can see there is no PDC in the circuit except for the fuses.

Please let us know what happens.

Cheers, Ken

Pull the switch out of the dash or at least get where you can look at the wires Ok find the brown it may not be hard to spot it will be the burnd up looking one take a test light and turn the switch on test lite the brown wire if you have no light pull the plug out of the switch I bet you will find it melted. The wire is not heavy enough to hold the load of the truck and the trailer. And if trailer was wired wrong it feed power to ground and burned the wire up. The brown wire is the whole key from front to back.(NOS)

I would suspect burned connectore on the headlight switch

Roy

The connector does not come with the switch. It is part of the main wire harness. Check all connections inside and look for burnt ends

Roy