| 摘要 |
PROBLEM TO BE SOLVED: To improve the accuracy in failure diagnosis of an EGR system to prevent the misdiagnosis. SOLUTION: This failure diagnosing device is provided with an EGR valve for adjusting the amount of EGR of an engine, the EGR system for controlling the operation of the EGR valve for adjusting the amount of EGR corresponding to an operating condition of the engine, an idle control valve for adjusting the amount of idling air of the engine, and a control means for controlling the idle control valve to keep the amount of idling air a predetermined value, opening and closing the EGR valve after the lapse of a predetermined time, determining the pressure difference between the intake negative pressure in opening the EGR valve and the intake negative pressure in closing the EGR valve, and determining the failure diagnosis when the pressure difference is less than a control value, when the failure diagnosing condition of the EGR system is satisfied.
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