| 摘要 |
PROBLEM TO BE SOLVED: To dispense with an atmospheric pressure sensor for detecting a change in atmospheric pressure, prevent a diagnosis region from being restricted to a low vehicle speed region, enable diagnosis in a vehicle speed region of normal running and even during running on a highland and a mountainous road to increase a diagnosis frequency, and detect the presence or absence of the leak of fuel evaporation gas with high precision. SOLUTION: When detecting the presence or absence of the leak of fuel evaporation gas in an evaporation purge system, attention is paid to the shrinkage/expansion of a fuel tank side and an engine side of the evaporation purge system separated by a PCV 15 from each other to the substantially same extent to the change in atmospheric pressure, a difference between pressure in the system while the PCV 15 is closed and pressure in the system while the PCV 15 is opened is calculated, and the influence of the change in the reference pressure of a relative pressure sensor brought by the change in atmospheric pressure in an evaporation generation amount measuring mode and a leak amount measuring mode is offset to diagnose the presence or absence of the leak to enable diagnosis in the vehicle speed region of normal running and even during running on a highland and a mountainous road in order to increase a diagnosis frequency and detect the presence or absence of the leak of fuel evaporation gas with high precision.
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