Electrical 2001 Silverdo

Did they work at one time, or is this a new installation?

The brake controller wiring harness changed between 2002 and 2003. You might be using a 2003-up wiring harness on the older vehicle. The difference is the location of the light blue and brown wires. Reverse them and give it a try.

IIRC... there is a fuse in your under hood electrical center devoted to this circuit. has nothing to do with the lights on the truck.

Everything worked until just recently. The trailer wiring is fine. The hazard warning lights on the truck do not work and the stop lights on the truck work but do not work at the trailer plug recepticle on the truck. The right and left turn pins on the plug work when activate but not when the brake is activated. Checked all the fuses. .