| 摘要 |
PROBLEM TO BE SOLVED: To provide comparatively many chances of failure diagnosis for an assist air supply system, and provide failure diagnostic results having high reliability. SOLUTION: Diagnostic conditions are judged to be set up when a control valve is controlled to be closed while an engine during its idling is in a stable operating condition and also an OFF signal is outputted to an assist air control valve (step S11), and reference fuel injection pulse duration Tp is read out so as to be recognized as control valve closing period reference fuel injection pulse duration ASOFFTp (step S12). Next, an ON signal is outputted to the control valve so that the control valve is controlled to be opened, and forcibly opened (step S13), and after the lapse of set time, the reference fuel injection pulse duration is read out so as to be recognized as control valve opening period reference fuel injection pulse duration ASONTp (step S14). Difference ΔTp between both reference fuel injection pulse duration ASONTp and ASOFFTp is compared with a set value Tpo (step S17), and when ΔTp<Tpo, it is diagnosed that an assist air supply system is abnormal (step S18). |
