| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method having high reliability in diagnosis for diagnosing an NOx sensor arranged in an exhaust gas region of an internal combustion engine and to provide an apparatus for executing the method and provide an apparatus for executing the method. <P>SOLUTION: Diagnoses (50) are executed while a control unit (30) is still operating after the internal combustion engine (10) is switched off and executed only when an excess air factor λ of exhaust gases exceeds a predetermined λ threshold which secures sufficient purification of the exhaust gas region (13) after the switch-off. On the basis of the diagnoses (50), when a reference signal for a measured NOx signal (NOx) and/or a characteristic value of the measured NOx signal (NOx) exceeds the threshold, it is determined that the NOx sensor (16) is at fault. The reference signal and/or the characteristic value can be further used for measuring signal offset of the NOx signal (NOx), checking diagnoses (52 and 54) to be executed during the operation of the internal combustion engine (10), and/or verifying validity. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
