Patent attributes
In a diagnostic apparatus for an evaporative emission control system having a fuel tank is hermetically sealed under negative pressure on the basis of target inner pressure, and leak of the evaporative emission control system is judged when a diagnosis value based on a pressure variation amount after the hermetical sealing under at least negative pressure is larger than a judgment value, ECU estimates an evaporated fuel generated amount on the basis of a tank inner pressure value at the start time of a diagnosis. When the evaporated fuel generated amount thus estimated is large, target inner pressure Pteb is set to a high value, and when the evaporated fuel generated amount thus estimated is small, the target inner pressure Pteb is set to a low value.
