Ok I have a 04 silverado, work truck model, with factory trailer wiring. and the left trailer light is not working at all. Running light does work but no blinker or brake light.
All lights on the truck do work. i have double checked the left trailer fuse and is forshure good.
and have unplugged the harness from the plug at the hitch andchecked for power and everything works but the wire for left turn / brake.

I just baught the truck a few months ago and the lights originally worked when i got it. i pull a trailer 2 to 3 times a week soo i kinda need to figure this out ASAP.

Thanks in advance