Hello all, I have had this problem too and mine is now hoepfully fixed! I have a 2013 fiesta Ecoboost 1ltr The light/warning kept coming on/going off so took it back 3 times. The final time i told them i did not want it back until i knew it was safe. They drove it around for a week as the diagnostic computer showed nothing. Eventually the light/warning came on whilst they had it and they plugged it in whilst the light/warning was actually showing on the car. This did give a Fault Code! Mine was something to do with the throttle body and has now been replaced. I only had it fixed this week but so far so good! I really hope this helps someone to get their car fixed too!