fail safe mode light on 2005 Ford Five Hundred

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
what causes fail safe mode light to come on every mile or so and completely shut the engine off?
(2) Answers
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.

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.