| 摘要 |
An abnormality diagnosis apparatus for an evaporative emission control system which includes a fuel tank, a canister for adsorbing evaporative fuel generated in the fuel tank, a charging passage for connecting the canister and the fuel tank, a purge passage for connecting the canister and an intake system of an internal combustion engine, a vent passage for opening the canister to atmospheric air, an evaporative fuel passage for connecting the fuel tank and the intake system, a first control valve interposed in the charging passage for opening and closing the charging passage, a second control valve interposed in the purge passage for opening and closing the purge passage, a third control valve interposed in the vent passage for opening and closing the vent passage, a fourth control valve interposed in the evaporative fuel passage for opening and closing the evaporative fuel passage, is disclosed. According to the apparatus, abnormality of the evaporative emission control system is diagnosed based on a detected pressure in the fuel tank. During the abnormality diagnosis, the fourth control valve is controlled to be maintained in a closed state, and the abnormality diagnosis is performed by changing an open or closed state of at least one of the first, second and third control valves without opening the first and third control valves simultaneously.
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