RFID Chips on Modern Car Keys, Test

Using a scanner tuned to 130 & 135kHz AM. I am listening to the different sounds this Toyota makes when I try different keys.
This is approximately how the RFID system works:
1. key is inserted and flips a switch inside the keyhole
2. the car emits energy in the form of radio waves to power the circuit located in the key itself (the RFID chip required no battery)
3. the key -- now energized -- transmits back to the car a secret code
4. after the car receives the code it expects it allows the car to be started

[@vidmojo]

that is most likely EMI. You need a RFID kit, like a USB dongle, to see what frequency is actually transmitting packets. They use simple challenge/response protocols based on proprietary cryptography/math. I'm interested in the specific frequency.