A method for activating a function of a motor vehicle upon detecting the presence of a user apparatus in a predetermined detection area around the vehicle. The method includes a step of determining the position of the user apparatus relative to the body of the user; a step of receiving, by the user apparatus, a signal comprising a broadcast message sent by the vehicle; a step of calculating a compensated value of the power of the signal received from the determined position of the user apparatus; a step of estimating the distance separating the user apparatus from the vehicle using the compensated power value, and a step of activating at least one function by the vehicle when the estimated distance is less than a predetermined threshold.