How do I change the battery in my car key?

you probly dont have a battery in it if they are chiped you need to have it reprogramed if you have code or a red master key if not you have to have a high grade chip that can read it which cost around fifty pounds or u need to take the immobilse of car or you need to take car back to ford and get programed of car imobliser cost around 100 pounds you could just have a light on it does it have a little black square in it?

del
April 2006