I have a 2003 2500HD and I am not getting a right turn signal at the trailer light connection by the hitch in the rear. The fuse was burned out, so I have replaced it, but still no right turn signal. The right turn signal works on the truck. Where should I start? Do I start at the fuse and work my way back to the rear of the truck, or do I start at the trailer connection and work to the front of the truck?