95 Z28--The ABS warning light comes on quite often and when on the brake pedal is hard and a few times when the ABS light is not on when I brake the Low Traction light comes on and the brakes don't work very well.

 

I had the same issue. I believe it is one of the wheel speed sensors. I never really checked it out, but I pulled my ABS relays and pulled the bulbs for my ABS Inop and Traction light. Never a problem since.

What's funny is that it only happened when it was warm outside.