The car works it out because as the battery voltage decreases , the output oscillator frequency of the key fob shifts a little ... this is how the car works out the battery is on the way out.
The key doesn’t transmit its status , other than sending the function command and the next code sequence generated by a pseudo-random number generator.
The car can work out it’s a known key because it knows the last pseudo-random number spat out from it... as it’s pseudo-random it knows what the next code sequence will be.
When you program the car , you’re just telling it the next number received will be a genuine number, after that the receiver know the next number from that fob. In a likewise way it can store another key.
Last edited by reinaldo_is_spam; 01-12-2017 at 05:50 PM.
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