My sister has a 2001 mustang GT. The Theft light comes on randomly and the car wont start. I assume it shuts the fuel pump off. In gm cars key cylidners are common for something of this type. Well i orderd one and see theres nothing to do with the theft system in the ingition cylinder. What detects the "key chip" on these things. I have to keys they will both do it so im assuming its not the keys and its something else. It just started acting up within the last month or so. Any help would be great.