| 摘要 |
PURPOSE:To reliably diagnose a trouble of an exhaust reflux device, by a method wherein a pressure at the upper stream of the exhaust reflux valve of an exhaust reflux passage is compared with a negative pressure by means of which the exhaust reflux valve is actuated. CONSTITUTION:When, based on a detecting value, e.g. a number of revolutions signal (a), a cooling water temperature signal (b), an intake air amount (c), it is decided that a diagnosing area is contained in an exhaust reflux area, a control unit 7 compares a detecting signal from a first negative pressure switch 4 for detecting a control negative pressure to an exhaust reflux valve 2 with that from a second negative pressure switch 6 for detecting a pressure at the upper stream of the exhaust reflux valve 2 in an exhaust reflux passage 1. When the exhaust reflux valve 2 is to be opened, i.e. when a negative pressure is detected by a first negative pressure switch 4, when a detecting signal from a second negative pressure switch 6 is below a working pressure, or in the converse case, a trouble of or leak past the exhaust reflux valve 2 is diagnosed to occur, and an alarm lamp 8 is actuated. |
