Hi there
there are two things that could go bad -the first is the stop lamp switch --make sure you have brake lamps--try it a dozen times--if you do not then chk the stop lamp switch and the conector to the stop lamp switch ---if that chk out ok --then you probely need a shift lock actuator cable,, they seize up,,, this cable runs from the steering column to the shifter --it runs about $60 and labor is about $250 to $300. ---Do you need any more info?
Ford Mechanic
ASE Master -Ford senior master-20 years experience