Encoded Ignition Key
WARNING: This page is about a different car, the 2000 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
When ignition switch is in START or RUN position, instrument cluster initiates the encoded ignition key interrogation process. Each encoded ignition key must be programmed into instrument cluster before it can be used to start the vehicle. This encoded ignition key is much larger in size to accommodate the electronics located inside plastic cover.