It could be as simple as the plug under the dash coming out. check that first, and also check the fuses, too.
An ABS check light is most often caused by the failure of a wheel speed sensors, but it can also be caused by the failure of the ABS module or wiring faults. It has nothing to do with the brakes or rotors, per se.
It could be your ABS sensors or your ABS pump. If it's just a sensor, you're in luck. If it'd the pump, then try to find someone who is willing to sell you one off a parts car that was known to be working. They are expensive new.
Clean your ABS sensors first. And go ahead and replace the relays. Both are cheap and easy to do. If not the pump sometimes fails.. But you want to make sure of that first. You could always test to see if your ABS works by finding something slick to brake on.. Low speeds and with no traffic would be good..
above is a summary of what I heard so far from various tech sources.
But where can I find those sensors/speed sensors...etc?