Ford Repair: ADVANCED TRAC LIGHT ON, ats system, four wheels

Question
Our 05 Freestar Advance Trac Light is staying on after driving a few miles from home. Road conditions are dry and smooth. The warning light remains on and when I do a system check it tells me there's a problem with the ATS. I've been told that this may be related to the ABS and certain connectors by each wheel or that certain wires are getting wet under-body. Any suggestions?

Answer
Dan, the ATS system uses sensors to operates on all four wheels.  My understanding, that these sensors are in addition to the ABS sensors.  I don't have a good way of checking them, however it seems that one of them is malfunctioning.  Either change all them or have them checked as of which one is not working.  Thanks!