| 摘要 |
PROBLEM TO BE SOLVED: To increase the reliability of diagnosis by considering a high-level change of automobile running made during diagnosis with respect to the evaluation of a pressure change and holding the diagnostic number of times. SOLUTION: When diagnosis is started, by the operation of a pressure changing means 2, a specified difference pressureΔPA with respect to an atmospheric pressure in a tank or a tank ventilation device is set. Simultaneously, an atmospheric pressure POE is measured by a high-level change specifying means 5. After the passage of specified time, a difference pressureΔPA and an atmospheric pressure POE are measured at the time of the end of the diagnostic process, a difference pressureΔPA-POA-(ΔPE-POE)=PTE-PTA, and at the end of the diagnostic process, an in-tank absolute pressure (PTE, PTA) of the diagnosis starting time is formed. Then, a difference PTE-PTA is compared with a threshold value, and if it exceeds the threshold value, leakage is estimated and, if not, the airtightness of the tank ventilation device or the tank is determined.
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