| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide technology capable of detecting abnormality when the abnormality occurs in a bypass passage bypassing a NOx catalyst. <P>SOLUTION: A bypass passage is provided so as to bypass a reducer adding valve, the NOx catalyst and an air-fuel ratio sensor provided in an exhaust gas passage in an order form an upstream. An integration value of drop quantity of detection value of the air-fuel ratio sensor is calculated when reducer is added from the reducer adding valve (S103). When the integration value of the drop quantity of the detection value of the air-fuel ratio sensor under a condition where it is assumed that separation ratio which is a ratio of flow rate of exhaust gas passing through the NOx catalyst and flow rate of exhaust gas flowing in the bypass passage is a target value, and actually calculated integration value are different (S104), it is determined that abnormality occurs in the bypass passage (S107, S108). <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
