Ignition key

Fig 1: Identifying Ignition Key Transponder

Courtesy of VOLVO CARS OF NORTH AMERICA.

There is a communication circuit in the ignition key, known as a transponder. This circuit is supplied with power from the magnetic field that is formed around the antenna ring when the central electronic module (CEM) activates the antenna ring. Consequently, the transponder is not dependent on a further power supply.

In order for the key to be used in the vehicle, a code in the key must be entered by the central electronic module (CEM). When the vehicle is delivered from the factory, two keys are normally programmed. When a key has been programmed for the central electronic module (CEM), the key is locked and cannot be programmed for another vehicle.