fail safe mode light

usally has to do with fly by wire system which replaces the old cable style. when there is a malfunction, the light comes on and the vehicle returns to dile with a slight increase to at least keep you moving to the side of the road. you say it shuts off completely?? it should not but there may be a couple of issues here. Roy

As Roy said, electronic throttle body concerns are fairly common for this first attempt at drive-by-wire in a Ford car (Ford Diesel Trucks have been using drive by wire for a while). Throttle position sensors are at issue, and the ETB itself. They had a back order on replacement parts for months back in 2009 on these.