1999 Chevy Suburban Light Problem

Greetings all. When I cut my lights on on my 99 Chevy Suburban, the Front lights come on but the Rear do not nor do my parking lights. I have replaced the both rear circuit boards and all six bulbs, still no lights. Brake, Reverse and signal lights work when I use the signal bar or the hazzards. I have checked the fuse inside and under the hood all appear to be good. PLEASE HELP.:shakehead:shakehead