METHOD FOR CONTROLLING ACCESS TO A MOTOR VEHICLE

A method for operating a passive access system for motor vehicles includes arranging multiple transmission antennas at different locations on a motor vehicle for sending out low frequency signals. A mobile ID transponder, formed by a 3D-receiving antenna assembly, receives the low frequency signals. The antennas send out time-delayed first signals and then simultaneously send out signals. A signal strength is detected by the 3D antenna assembly in the ID transponder for each spatial direction. Information related to the space-direction-dependent signal strengths is transmitted from the ID transponder to the motor vehicle. Depending on the received information, the transmission signal strengths are adjusted. Then, further low frequency signals are sent, and received in the ID transponder. Based on further signal strength information, a plausibility check is performed in order to detect an extension of the signal path between the motor vehicle and the ID transponder via intermediate stations.