| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technology capable of detecting or determining degradation of a NOX sensor in a construction in which the NOX sensor is disposed in an exhaust passageway downstream of a selective reduction catalyst. <P>SOLUTION: A degradation detection system includes: a three-way catalyst disposed in the exhaust passage of an internal combustion engine; the selective reduction catalyst disposed in the exhaust passage downstream of the three-way catalyst; and a NO<SB POS="POST">X</SB>sensor disposed in the exhaust passage downstream of the selective reduction catalyst. A rich process is executed that is a process for causing an air-fuel ratio of exhaust flowing into the three-way catalyst to become rich, and it is determined that the NO<SB POS="POST">X</SB>sensor has degraded on a condition that a measurement value from the NO<SB POS="POST">X</SB>sensor does not reach nor exceed a threshold value within a prescribed time that follows the start of execution of the rich process. <P>COPYRIGHT: (C)2012,JPO&INPIT |
