I just bought a 2001 silverado 2500 HD and when I start the truck the head lights automatically comes on and can't be shut off unless the truck is shut off.
The day time running lights don't come on at all and I already changed the bulbs and checked the fuse but not the relay.

Their is a new wire harness for a plow installed also.

Any advice on what to check, could the plow harness have something to do with it?