ABS & brake light coming on in Astro Van-makes whining noise and "hesitates" when press on brakes?

It doesn't happen all the time-the lights would go on and off and the noise and hesitation didn't happen all the time either. When I took it to the dealership they couldn't figure it out, and referred me somewhere else. Now the lights stay on ,but the breaks aren't "hesitating & whining". Any ideas?