Introduced in the mid-1990s, transponder keys were developed in response to a need to make cars more difficult to break into. Most modern cars come with a transponder key.
In addition to the traditional key which is cut to match your car’s locks, a transponder key has a small transponder or microchip contained inside. This is coded to an ECU (electronic control unit) in your car. Each time you use your car the key sends a special code to the vehicle which has to be confirmed for the car to start. Because the car cannot be started without the authorization it cannot be hotwired by thieves.
Most transponder keys also allow remote locking and unlocking of your car and some can be used with keyless entry and push button start/stop systems.