| 摘要 |
The method detects the absence of a catalyst 281 of a selective catalytic reduction (SCR) system 280 of an internal combustion engine 110, preferably of a diesel powered motor vehicle 100. The catalyst is located in an exhaust pipe 275 of the engine and the method comprises the steps of: determining a value of a parameter indicative of a flow resistance of exhaust gas through the catalyst; and identifying an absence of the catalyst if the determined value is lower than a reference value when compared (805, figure 3). Ideally the value is a mean value (804, figure 3) calculated from a plurality of values (803, figure 3) obtained over time. The values are preferably calculated based upon a formula that uses measurements of (i.) differential pressure of exhaust gas across the catalyst and (ii.) an exhaust gas volumetric flow rate through the catalyst in combination with a correction factor calculated as a function of a catalyst temperature. Preferably the value is only calculated when a differential pressure across the catalyst and a volumetric flow rate through the exhaust pipe are greater than respective predetermined values (801,802, figure 3). |
