Daytime runners and headlights DON'T WORK

I have a 99 gmc k3500 and my daytime runners and head lights aren't working. My running lights all work, and my brights works. I have replaced the bulbs, the fuses, and the light switch still nothing. dealer can't find problem, and niether can I.
can somebody please help
thanks
chris :banghead:

Maybe the DRL controller module is bad?

Also, most parking brakes have a switch which shuts off the DRL's when the parking brake is applied. This switch may have malfunctioned or the parking brake pedal or lever is not releasing all the way.

I had the same problem, ended up cutting the blue wire comeing from the headlights and bypassed the DRM by just grounding it to the chasis Who needs lights in the daytime anyway?