METHOD FOR ACTIVATING A MOTOR VEHICLE FUNCTION AND ASSOCIATED ACTIVATION DEVICE

A method for activating a function of a motor vehicle by an activation device, using a portable access device carried by a user. The activation of the function being initiated by detection of the presence of the user in a predetermined area around the vehicle, and in accordance with a result of authentication of the portable access device by the vehicle, the method including: A) the detection of the presence of the user in the predetermined area is implemented by a predetermined profile of ultra-wideband radiation emitted by the activation device in what is known as an ultra-wideband reflective mode and reflected by the user, and B) the authentication of the portable device is implemented by a bidirectional ultra-wideband communication between the activation device and the portable access device.