| 摘要 |
<P>PROBLEM TO BE SOLVED: To diagnose abnormality of quality of a reducing agent solution with a relatively simple constitution. <P>SOLUTION: This exhaust emission control system has a urea water tank 21 for storing urea water of the predetermined concentration, and an SCR catalyst 13 arranged in an exhaust passage of an engine and selectively reducing NOx in exhaust gas by the urea water, and adds the urea water to the exhaust upstream side of the SCR catalyst 13 by a reducing agent adding valve 15. A urea water level sensor 31 is also arranged as a liquid quantity detecting means for detecting a liquid quantity in the urea water tank 21. An ECU 40 diagnoses the abnormality on the quality of the urea water based on a comparison result between a stopping time liquid quantity detected by the urea water level sensor 31 when stopping the engine and a starting time liquid quantity detected by the urea water level sensor 31 when starting the engine next time. <P>COPYRIGHT: (C)2010,JPO&INPIT |
