brake and turn signal light failure

I have a 98 chevy silverado pickup with a v-8 350 motor 84,000 miles. the brake lights, turn signals and hazard lights stopped working. i have checked the fuse and replaced the flasher relay no help, also cleaned ground wire for tail lights. i unhooked the tail light plug to see if there was a short in them the turn signals on the front of truck still wouldn't work. is there a power distribution center or relay that provides power to this system and if so where is it located? Thanks for your help, :) bass man