Ford has had an issue with the wiring harness somewhere between the front of the truck and the trailer plug. On my 2002 F350, I had to abandon the wire in the harness and wire the trailer clearance lights into the tail light circuit on the truck. Never had anymore issues.
Amateur Radio Operator (KE5DFR)|No Longer Full-Time! - 2023 Cougar 22MLS toted by 2022 F150, 3.5L EcoBoost Tow Max FX4 Lariat Travel with one Standard Schnauzer and one small Timneh African Gray Parrot, retired mechanical engineer