Methode for detecting the absence, inside and surrounding the vehicle, of portable control devices of a passive entry system for vehicles

The method involves activating (B1) the periodic monitoring (b) of a portable remote control box of a hands free access system of a vehicle e.g. car, during receiving of identification signal from the portable remote control box. Absence of the portable remote control box in a predefined covering area extending in and around the vehicle, is confirmed (c) in case of absence of response to identification request signals during identification (a) of the portable remote control box by a CPU embarked in the vehicle.