| 摘要 |
PURPOSE:To prevent misoperation of a lean monitor, by cancelling a measuring time before the time when feedback control is released during the measurement of a time (monitor time) in which a lean condition of an air-fuel ratio sensor output is connected. CONSTITUTION:Feedback control of an injector 30 is operated in accordance with an output of an air-fuel ratio sensor 34 by a digital control circuit 54. While here a time of duration under a lean condition of the output of the air- fuel ratio sensor is monitored, if the monitored time reaches at least a prescribed value, a lean monitor is operated to release feedback control. In this way, an overrich state of air-fuel ratio due to a trouble or the like of the sensor is prevented. During the measurement of a lean monitored time, if the feedback control is released, a measured time before the above release is cancelled to control to remeasure the time after entering again the feedback control. |
