Abstract: A method for controlling mobilizing and immobilizing a vehicle using a valid passive entry-passive start key includes detecting that a vehicle operator exits the vehicle, determining that the key is absent from the vehicle, automatically immobilizing the vehicle by preventing vehicle propulsion; if a power source of the vehicle is immobilized after the operator exits the vehicle, automatically mobilizing the vehicle to allow vehicle propulsion when a key authorized to operate the vehicle is detected in the vehicle after a vehicle door is opened and closed, and automatically placing the vehicle in a low energy consumption operating state, if a reference period expires after the operator exits the vehicle with the power source running.