The engine immobilizer system prevents the car from being stolen.
When you insert the key into the ignition switch, the transponder chip in the key head transmits an electronic signal code to the car. The engine will only start if the electronic code in the chip matches the registered identification code for the car.
The system is automatically set when the key is removed from the ignition switch. Inserting a registered key into the ignition switch will automatically cancel the system that enables the engine to start.
In order for a Toyota dealer to make a new key with a built-in transponder chip, he will need the key number and the master key. But there is a limit on the number of additional keys that a Toyota dealer can make for a car owner. If you make a duplicate key yourself, you will not be able to cancel this blocking system and start the engine.
(The original version is published on the website ToyotaMan.ru)