That is your cheapest option. Your computer has to be programmed with the particular key and ignition switch you are using. It's part of the Passive Anti-theft System (PATS) that your car is equipped with. You could buy a programmer ($399) to shut off the PATS but that is more expensive than letting Ford take care of it.
I got two remotes w/keys for mine, but one remote died 6 months after I got it, so now I'm down to one. I need to get a new batt for it before this one dies, or it's coat hanger / brick time!
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