Key Programming

It usually requires a diagnostic tool and security access. Lost keys can be deleted from the car. Some brands require dealer programming. Some cars allow adding a key yourself if you have two working keys; others need a code from the manufacturer. Key fobs are often programmed separately for remote locking.

The key's transponder code is stored in the immobilizer.

Keep a spare key; programming without one costs more. Unprogrammed keys may open doors but not start the car.