Method for detecting an identifier (Id) inside or outside a motor vehicle, said motor vehicle comprising a primary antenna and a primary processing unit, said identifier (Id) comprising a secondary antenna and a secondary processing unit, wherein said detecting method comprises: - cyclic transmission by one of the two primary or secondary antennas (A1, A2) of a plurality of signals, Sg1, over a plurality of communication channels; - cyclic reception by the other of the two primary or secondary antennas (A1, A2) of said plurality of transmitted signals, Sg1; - performance by one of the two secondary or primary processing units (U2, U1), for each communication channel, of a plurality of measurements, RSSI, of a power of said plurality of received signals, Sg1', corresponding to said plurality of transmitted signals, Sg1; - for each communication channel, comparison by one of the two secondary or primary processing units (U2, U1) of a combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel: - with a primary threshold power of passage from inside to outside the motor vehicle, said primary threshold power being different from one communication channel to another; and - with a secondary threshold power of passage from outside to inside said motor vehicle, said secondary threshold power being different from one communication channel to another; - if, for at least one communication channel, said combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel is greater than or equal to said secondary threshold power, said identifier (Id) is detected as being inside said motor vehicle, otherwise said identifier (Id) is detected as being in its previous state, inside or outside; and - if, for at least one communication channel, said combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel is less than or equal to said primary threshold power, said identifier (Id) is detected as being outside said motor vehicle, otherwise said identifier (Id) is detected as being in its previous state, inside or outside. - cyclic transmission by one of the two primary or secondary antennas (A1, A2) of a plurality of signals, Sg1, over a plurality of communication channels; - cyclic reception by the other of the two primary or secondary antennas (A1, A2) of said plurality of transmitted signals, Sg1; - performance by one of the two secondary or primary processing units (U2, U1), for each communication channel, of a plurality of measurements, RSSI, of a power of said plurality of received signals, Sg1', corresponding to said plurality of transmitted signals, Sg1; - for each communication channel, comparison by one of the two secondary or primary processing units (U2, U1) of a combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel: - with a primary threshold power of passage from inside to outside the motor vehicle, said primary threshold power being different from one communication channel to another; and - with a secondary threshold power of passage from outside to inside said motor vehicle, said secondary threshold power being different from one communication channel to another; - if, for at least one communication channel, said combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel is greater than or equal to said secondary threshold power, said identifier (Id) is detected as being inside said motor vehicle, otherwise said identifier (Id) is detected as being in its previous state, inside or outside; and - if, for at least one communication channel, said combination, Cb, of said plurality of power measurements, RSSI, performed on said communication channel is less than or equal to said primary threshold power, said identifier (Id) is detected as being outside said motor vehicle, otherwise said identifier (Id) is detected as being in its previous state, inside or outside.