| 摘要 |
PURPOSE:To prevent a false diagnosis due to a change of a starting state by deciding a failure of EGR when temperature in an EGR passage is less than a designated value determined according to cooling water temperature or intake air temperature at the time of starting in an operating state where EGR is to be conducted. CONSTITUTION:Negative pressure from an intake tube negative pressure take- out port 34 is introduced into a diaphragm chamber 27 of a diaphragm device 25 for driving a valve element 24 of an EGR valve device 20 through a temperature sensing valve 32 adapted to open when water temperature is more than a designated value and a negative pressure control valve 30 operated in response to exhaust pressure. A microcomputer 50 to which detection values of an engine speed sensor 56, a water temperature sensor 57, an intake air pressure sensor 58, a temperature sensor 59 disposed in an EGR passage 13 and an intake air temperature 62 are input is adapted to decide a failure of EGR when a detection value of the temperature sensor 59 is less than a designated value determined according to cooling water temperature and intake air temperature at the time of starting in an operating state where EGR is to be conducted according to intake pipe negative pressure, engine speed and cooling water temperature. |
