| 摘要 |
PROBLEM TO BE SOLVED: To detect opening sticking failure of a flow passage switching means by existing equipment without adding new components. SOLUTION: A switching valve 15 arranged in a fuel return line 3b is normally in a closing state. Excessive fuel is returned to a fuel tank 4 through a fuel by-pass line 3c. The opening sticking failure diagnosis of the switching valve 15 is executed by comparing a fuel temperature integral value CFTMP calculated on the basis of the fuel temperature FTMP in the fuel tank 4 detected by a fuel temperature sensor 6 and an integral value CFTCAL of an estimated fuel temperature FTCAL calculated on the basis of parameters expressing operating states of a vehicle such as an intake air quantity GA detected by an intake air quantity sensor 10, engine rotation speed NE detected by an engine rotation speed sensor 12 and vehicle speed VSP detected by a vehicle speed sensor 17. When the difference therebetween is a predetermined value or more, the device estimates that excessive fuel passes through a fuel delivery line 3a to be returned to the fuel tank 4 with its temperature increased, and diagnoses the switching valve 15 as opening failure. COPYRIGHT: (C)2005,JPO&NCIPI
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