trailer marker lights not working

Hey everybody! keep it short and sweet.
hook up any trailer, brake and turns will work. Marker lights wont. I'm pretty sure based on my internet reading that I have a corroded wire some where on the trucks end. Just wondering if anyone else has had this happen to them. i'm gonna check the fuses tomorrow and maybe crawl under the truck. looking for any pointers.
i have a 2006 dble cab turd sport with factory tow package.
cheers eh

 

90% of trailer light problems are a bad ground.

 

All of them including the rear tail lights? Slide the cover off the plug pin 3 brown wire, got power then go after the trailer wiring.

 

Loose fuse in engine bay. Swapped with a new one. Everything is working good so far