While driving on a very mountainous, winding road, the steering became stiff as I was in the middle of navigating a corner. For a few moments, the steering was completely unresponsive, before I was able to regain control with much force and effort. As I regained control of the vehicle, a warning light came on, which indicated: "System check, Steering Assist Fault, Service Required." I tried basic trouble shooting, but could not check the power steering fluid levels and the fuse that controls the system was in good working order. My normal mechanic stated that this must be serviced by Ford. The vehicle is putting out a code, but the mechanic and O'Reillys were not able to get the code to read. The loss of power steering assist, in the area I was in, nearly caused me to drive in to a creek. Unexpected loss of power steering caused me to Jam my wrist while trying to keep control of the vehicle. Iced the wrist but it is still sore. Seeking medical treatment in the AM Vehicle (less than 4 years old) has now had: 1) cannister purge valve issue resulting in an out of pocket fix (this car not covered under canister purge recall) 2) clutch forks and clutch assembly issues 3) power steering assist issues