My 2011 5.0 has gotten this problem twice now! The first time at 1720 miles on the odometer. I took it to the dealer and he did the check that is detailed in the workshop manual pages attached to the earlier reply and reset the light. It now has 2230 miles and has done it again! There are no obstructions anywhere in the intake or exhaust so, according to the workshop manual pages, it must be an "engine mechnical concern" (that doesn't sound good), a "damaged or sludged electronic throttle body" (with ony 2230 miles on it I find that hard to believe), a vacuum leak (possible, but with a new car it has to be a bad hose or something), or a damaged PCM (again, with a new car could be a lemon PCM). Anyway, its back to the dealer tomorrow with a "Don't give it back until you figure out what is wrong, and don't just reset the light and assume it's fixed". Shouldn't happen on a brand new Mustang!!!!!!
Anyone have any other ideas?