System for filling at least one tank, motor vehicle comprising such a system and method for implementing such a system

A method for implementing a filling system for filling at least one tank of a motor vehicle, the filling system comprising:

• a casing secured to the motor vehicle;
• at least one filling head arranged in the casing and connected to a urea tank;
• a removable cap suitable for closing off or freeing the filling head for filling the urea tank;
• and
• a movable flap suitable, during closure thereof, for covering the filling head for filling the urea tank and the cap closing off the filling head for filling the urea tank;
• wherein when the cap is positioned in a housing formed to that end in the casing, the closing of the flap is prevented, whereas when the cap closes off the filling head, the closing of the flap is authorized such that the flap covers the filling head and the cap closing off the filling head.