| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect an abnormality when the abnormality occurs during a switching operation between a first measurement state in which air is used for a gas flowing in a measurement passage and a second measurement state in which a mixture including fuel vapor is used for the gas flowing in the measurement passage. SOLUTION: The behavior of the change of a first pressure P0 after starting the measurement of the first pressure P0 in the first measurement state and the behavior of the change of a second pressure P1 after starting the measurement of the second pressure P1 in the second measurement state are measured by using a three-way valve 21 changing over between the first measurement state and the second measurement state and a pressure sensor 24 measuring the pressure produced by a restrictor 23 in a measurement line 22. When the behaviors of the changes of the first and second pressures are considered to be substantially identical to each other by the comparison of these behaviors, the switching operation of the three-way valve 21 is determined to be defective. COPYRIGHT: (C)2007,JPO&INPIT
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