Programming automotive keys is as much an art as it is science 

Modern vehicles use keys with electronic components called transponders (which is also called chip key), which is an electronic authorization device that allows operation to the vehicle when the correct electronic sequence is present. Each key fob contains a unique set of electronic serial numbers that communicates directly to the car’s engine control unit (ECU) through different means, including 125kHz low frequency RFID or through VHF in case of passive keyless entry (PKE) systems. Each vehicle is equipped with a list of serial IDs that it recognizes and accepts commands from. 

To secure the communication between keys and key programmers, OEMs safeguard the serial IDs with access protocols and security layers to deter bad elements. A number of tools are available to allow the keys to communicate with the ECU, which this article provides. Once access requests from the key programmers are verified to be legitimate and authority is provided, an encrypted serial number consisting of the manufacturer key and the seed is transferred from the chip key to the ECU, allowing reprogramming, cloning, and diagnostics functions to be performed.