I lost my one fob in the forest (I'd lost the other years ago), so I was stuck 3 hours from my home. The locksmith gave me the choice getting OEM or aftermarket fobs. The difference in price was astronomical. I chose the latter, and he came up with them and programmed them at my car, and now I have two fobs that work great and are functional in every way, other than the fact these "immobilization malfunction" alarms play out repeatedly for the first 5 minutes I'm driving the car. They do stop after a bit, and so I think I could survive having to listen to this long term, but I'd rather find a way to clear the warning without having to pay the utterly ludicrous markup that Ford puts on the price of their fobs.