Method for testing the functionality of a tank venting system of a motor vehicle having an internal combustion engine

A method for testing a functionality of a tank venting system of a motor vehicle having an internal combustion engine, including a controllable tank venting valve connected to an intake manifold, and including at least one pressure source for testing a tightness of the tank venting system using one of an overpressure and underpressure, the method comprising:

• testing a functionality of the tank venting valve via its activation in at least one of an opening and a closing manner during pressurization of the tank system using one of an overpressure and underpressure and by registering and evaluating at least one operating variable of the pressure source,
• wherein the tank system is pressurized using one of an overpressure and underpressure and the at least one operating variable of the pressure source is registered and evaluated during operation of the internal combustion engine;
• registering the operating variable of the pressure source while the tank system has a fluidic connection to the surroundings, and storing the registered operating variable as a comparison value;
• introducing one of an overpressure and underpressure into the tank system;
• opening the tank venting valve and registering the operating variable of the pressure source during an opening of the tank venting valve;
• and
• comparing the registered operating variable to the comparison value and drawing conclusions about the functionality of the tank venting valve and a functionality of a connection of the tank venting valve to the intake manifold based on the comparison.