tony, the keys have two completely separate functions. first, there is an RFID "pill" that is part of the immobilizer system. second, there is a transmitter that locks/unlocks the doors and arms/disarms the alarm system. these two systems are independent of each other.
the RFID pill is passive. it has no power source per se. its antenna receives a coded message from the corresponding antenna near the key cylinder. by induction, it creates current in the pill which the chip uses to process the message and create a coded reply which is transmitted by the same tiny antenna.
the circuit board is powered by the battery and activated by the button press. it sends out a coded message to the car. it does not receive anything.
both of these systems must be "known" by the car's computer. so if you got a new circuit board, it must be introduced to the car.
there is nothing in the keys themselves that is programmed. they have permanent codes which must be programmed in the car's computer so that the car recognizes and accepts that key.
your car still recognizes the RFID pill but of course, not the new circuit board. this new board must be programmed in the car computer. i don't know the procedure for doing that but surely someone else here does.
let me know if my above explanation was not clear.
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MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige.
Bought June 2000 - Sold May 2010