whenever i hook up a trailer to my truck, i have 2 different ones, i can shut the truck off, get out, and unplug the 4pin connecter, and my brake lights will stay on in my truck until i mess with the lights and brakes and it goes off. i usually turn the headlights on and off a few times and tap the brake pedal a few times and it goes off. i dont have a clue what it is, its a brand new plug in wiring harness, and i swapped it out and it wasnt it, maybe a bad ground location?

 

bump

 

Sound like the brake light switch.