2001 ford windstar lx abs light

My wife is driving a 2001 windstar lx, the ABS light has come on. It seems to drive fine and the brakes are still working, where do I start? I would like to fix it myself if possible.

A quick forum search came up with this:

http://www.automotiveforums.com/vbulletin/showthread.php?t=528271&highlight=abs+light

When I do the brakes and wheel rotations I check the sensors to make sure they're clean. Let us know what you find out.