| 摘要 |
The invention relates to a method pertaining to an SCR system whereby reducing agent is supplied to an exhaust flow upstream of an SCR catalyst (260), the content of NOx in the exhaust gases is measured upstream and downstream of the SCR catalyst (260) and any presence of reducing agent crystals in the SCR catalyst (260) is detected. The method comprises the steps of first shutting off the supply of reducing agent to the exhaust flow so that the SCR catalyst is substantially emptied of vaporised reducing agent, and thereafter, at a temperature at which reducing agent crystals vaporise, measuring NOx contents upstream and downstream of the SCR catalyst. The values are compared with one another and if a difference between measured NOx contents exceeds a certain value is taken as an indication of presence of reducing agent crystals in the SCR catalyst. The method comprises also determining that the NOx contents are correctly measured, and - concluding that reducing agent crystals are present, provided that the NOx contents are correctly measured and the presence of reducing agent crystals in the SCR catalyst (260) has been indicated. The invention relates also to a computer programme product comprising programme code (P) for implementing the method. The invention relates also to an SCR system and a motor vehicle (100, 110) equipped with the system. |
