An ultra-high frequency-based method for activating a function of a vehicle with a portable item of user equipment having an accelerometer. The method including the following steps: Comparing signals from the accelerometer with a predetermined signature; Detecting a characteristic movement of the portable item of equipment, associated with a command to activate a function of the vehicle, performed by the user on the basis of the result of the comparison; Checking the establishment of ultra-high frequency communication between the portable item of equipment and the vehicle, i) If communication is established, then transmitting a command to activate the function of the vehicle to the vehicle in order to activate said function, ii) If not, if communication is not established within a predetermined time interval following detection of the characteristic movement, then the method is stopped.