get ur self a code reader i got one from the motorbookguy.com obd 2 code scanner save you having to pay to have a code read out every time the light comes on and they give you a list of all the major codes and more from ford and whatever type of car u have u can also up grade the scanner on the net with programme down loads. $130 dollars pretty cheap especially if u have to get the codes out often
Could be for any of many reasons. Get your car to the garage and have the faults(s) read. Might just be a faulty sensor, might be an genuine problem, you'll only know when it's been looked at.
Probably just an oxygen sensor. Why don't you take it by AutoZone, or Advance Auto Parts? They will check it for free and tell you what the problem is.
Id book your car into a ford dealer...although light is on and cars running fine...what if engine blew up? especially if your warranty has ran out....definately book it in!
Chances are that if you don't get it checked you will cause damage to something else. It might only be a fifty dollar fix right now but it could certainly get worse. These lights don't just come on for no reason. The computer is telling you there is a problem with one of the sensors and it should be looked at. I don't know where your at but most local parts stores will check this for free and at least tell you what it could be.