I found this brown wire hanging from the back driver side of my truck, almost directly underneath the tail light. It seems to run back forward to the front but I can’t tell what it connects to at the back of the truck.

2008 Silverado 2500 4-Door Short Box with a 6.0 Vortec

 

The factory uses a brown wire at the rear for parking lights but should be in a loom unless it has been messed with over the years for some reason. Is it possible it has been added and not o/e? Possibly for a trailer. Just a thought.