| 摘要 |
PURPOSE:To prevent a false diagnosis at the time of high temperature by deciding a failure of EGR when temperature in an EGR passage is less than the first designated value and normality thereof when the temperature is more than the second designated value higher than the first designated value 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 micro-computer 50 to which detection values of an air flow meter 3, an engine speed sensor 56, a water temperature sensor 57 and a temperature sensor 59 disposed in an EGR passage 13 are input is adapted to decide a failure of EGR when a detection valve of the temperature sensor 59 is less than the first designated value (e.g. 100 deg.C) and normality thereof when the detection value is more than the second designated value (e.g. 150 deg.C) higher than the first designated value in an operating state where EGR is to be conducted. |
