Method for secure access to a motor vehicle

A method for securely accessing a motor vehicle whose opening elements are locked and unlocked through wireless communication between a portable access device and an access control module on board said motor vehicle, said portable access device comprising a motion sensor, the method comprising:

• authenticating the portable access device with the access control module,
• unlocking the motor vehicle when the portable access device has been authenticated,
• periodically transmitting, by way of the access control module, an interrogation signal into at least part of the passenger compartment of the motor vehicle intended for the portable access device following unlocking of the motor vehicle,
• upon each reception by the portable access device of said interrogation signal, triggering a first timeout a duration of which is greater than a transmission period of the interrogation signal,
• deactivating the portable access device when the first timeout has expired and an immobile state of said portable access device is detected by the motion sensor, wherein the immobile state of the portable access device is detected when the motion sensor does not detect any motion for a duration of a second timeout.