Both my turn signal lights are dimly light when my headlights are on and as I hit the brake they get brighter. Also when my headlights are on my horn doesn't want to honk and when I lock my truck with the keyfob it makes a slight honk.

I'm at a loss for what it is. I've checked the taillight harness and didn't see anything wrong with it. Is the horn on the same circuit as the flashers or something? Thanks in advance

 

Sounds like your turn signal lights have a short to voltage on the brake lamp circuit. Give all connectors and wires a look to see if there is something obviously wrong. Otherwise, you should begin with tracing wires from end to end. Turn signals are triggered at the BCM, so that might be a place to start.

 

Thanks...I'll give it a once over and see what I can find

 

Check the tail light junction box behind the bumper.