The present invention concerns a method (PR) for detecting an identifier (Id) for starting a motor vehicle (V), said motor vehicle comprising a first antenna (A1) and said identifier (Id) comprising a second antenna (A2). The method (PR) is characterized in that it comprises: transmitting, by said first antenna (A1), a first Bluetooth Low Energy™ signal (Sg1) to said identifier (Id) at a nominal power (P1); measuring the power (P1′) of said corresponding signal (Sg1′) received by the second antenna (A2) of said identifier (Id); comparing said measured power (P1′) with a threshold power (Ps), said threshold power (Ps) corresponding to a threshold distance (ds) from said first antenna (A1) that is less than the radius (r1) of a circle (C1) inscribed within the passenger compartment (H) of the motor vehicle (V), said circle (C1) being centered on said first antenna (A1); authorizing the starting of the motor vehicle (V) if the measured power (P1′) is greater than or equal to said threshold power (Ps).