Method for the diagnosis a tank ventilation valve

An electronic control device for testing an operability of a tank vent valve between an internal combustion engine and a fuel vapor reservoir, comprising:

• an arrangement for supplying a stored fuel vapor from the fuel vapor reservoir to the internal combustion engine when the tank vent valve is open, a fuel vapor supply representing a first energy flow to the internal combustion engine;
• an arrangement for allowing air to flow to the internal combustion engine through a throttle valve, a second energy flow being assigned to the air, the second energy flow being defined as a product of the air flowing through the throttle valve and an efficiency with which the air is burned after being mixed with a fuel;
• an arrangement for holding a sum of the first energy flow and the second energy flow to a predefined value when the tank vent valve is controlled in an opening manner;
• an arrangement for controlling the tank vent valve by performing an opening control;
• an arrangement for determining a change in energy flow through the throttle valve, resulting from the opening control;
• an arrangement for comparing the change in energy flow to a predetermined threshold;
• and
• an arrangement for evaluating as a fault the change in energy flow when the change in energy flow is small and does not exceed the predetermined threshold.