My bet is bad hub bearings, But honestly if the light is on the system is NOT WORKING..... if you need the ABS and it doesn't kick in and you wreck, it is your fault...period !!!
Yea I found the trouble shooting codes for it when I had a guy at Advance Auto hook up a OBDII Sensor gizmo. Looks like it is coming from the right front sensor wire. It says loose connection. I looked up and down that line and saw no breaks in the line nor the connections loose. I'm having my auto mechanic take a crack at it before I have Ford look at it.