Most keyless start systems have a backup physical key[1] hidden inside the remote fob and will use very short range RFID [2] similar to older physical turn keys

Most keyless start systems have a backup physical key[1] hidden inside the remote fob and will use very short range RFID [2] similar to older physical turn keys and their immobiliser chips to authenticate with the car ECU and allow the engine to start. [1] https://static.cargurus.com/images/site/2016/03/21/20/42/pic-3533884746378553322-1600x1200.png https://static.cargurus.com/images/site/2016/03/21/20/42/pic... [2] https://www.mazda3revolution.com/threads/if-the-battery-in-the-remote-dies-start-the-car-by-touching-the-push-button-with-it.195610/ https://www.mazda3revolution.com/threads/if-the-battery-in-t...