ABS Light

My roommate has a '94 Int. LS 2 door 5 speed with 130k mi. The ABS light is on and the ABS is not functioning at all. What is the most likely cause of this?
I believe that it is due to a broken ABS sensor at one of the wheels. Is there a way to isolate each sensor to locate the non-functioning one?

Thanks

Probably, but even if you DID manage to isolate the malfunctioning sensor, would either of you know how to fix it?

Just take it to a mechanic.