How does the "Pass key security System" work on cars?

Answer 1

Depending on the year of car the original pass key system with the chip reads the resistance across the chip and this resistance is seen by the passlock module. If the Resistance is correct the car starts.
The newer cars with passlock 3 system each key has its own code and the passlock module is open for a new code for only 30 second after starting with an original or programmed key.
Once programmed the key should always work.
If you try to start a car with an unprogrammed key it will lock the passlock module and the vehicle must be towed in and unlocked by a dealer. Very time consuming and expensive.