does a 2007 mustang have a chip in it's key
Yes. If you still have the TWO original master keys you can program it to accept a new key (or keys), but if you only have one (or none) of the original chipped keys you have to go to the dealer for any new keys. There's a procedure in the owner's manual on how to add new keys, but again it requires you to have two keys already programmed on hand. I don't have a manual handy, it should give you all the info on how/what you can do as far as adding/replacing keys.
You can download the manual@ (page 82) http://owner.ford.com/servlet/ContentServer?pagename=Owner/Page/OwnerGuidePage&year=2007&make=Ford&model=Mustang
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