| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce the cost of a device as a whole, and to prevent wrong diagnosis, without fail, in an abnormality diagnosis apparatus of an NOx sensor, that is arranged at a downstream side of an NOx catalyst section for changing oxygen concentration in exhaust under prescribed conditions in the exhaust passage of an engine, has a pump cell for pumping out an amount of oxygen corresponding to the application voltage from an exhaust take-in space, and detects NOx concentration in the exhaust, by detecting the value of the current flowing to the pump cell, according to the amount of oxygen that has been pumped out. <P>SOLUTION: In an ECU, oxygen concentration in exhaust around the NOx sensor is calculated as that equal to the oxygen concentration at an upstream side of the NOx catalyst section, an abnormality diagnosis of the NOx sensor is performed, based on the calculation concentration; and it is determined whether the difference at the level of a prescribed level or higher is generated, in oxygen concentration in exhaust between upstream and downstream sides of the NOx catalyst section, while sandwiching the NOx catalyst section (determination of steps SA4 and SA12 is executed), and the abnormality diagnosis is prohibited, when it is determined that there is a difference at the level of a prescribed level or higher. <P>COPYRIGHT: (C)2010,JPO&INPIT |
