i have a problem starting my 55 plate 1.25 fiesta. when i turn the key the normal warning lights all come on but the car will not crank over. then the symbol of a car and padlock starts flashing. i try de activating it with the key but nothing happens. then after a few attemps the car starts. it will run for 30 secounds before cutting out. the symbol re appears and the car will not crank over again. anyone got any ideas.