Process for testing a plurality of components of an exhaust gas aftertreatment system

A process for testing a plurality of components of an exhaust gas aftertreatment system, wherein the plurality of components comprises a first SCR catalyst and at least one further SCR catalyst arranged downstream of the first SCR catalyst in the flow direction of exhaust gas to be passed through the exhaust gas aftertreatment system,

• a first NOx sensor assigned to the first SCR catalyst and at least one further NOx sensor assigned to the at least one further SCR catalyst, and
• a first DeNOx element assigned to the first SCR catalyst and at least one further DeNOx element assigned to the at least one further SCR catalyst, and wherein the process comprises at least the following steps:
• a) conditioning the SCR catalysts, wherein the SCR catalysts are heated above a predetermined threshold value to empty them of reductants using an internal combustion engine,
• b) testing the NOx sensors, wherein if a deviation of measured values determined by a respective NOx sensor from a reference value is greater than a predetermined threshold value the respective NOx sensor is marked as defective,
• c) testing the DeNOx elements, wherein if a change in measured values determined by a respective NOx sensor caused by an amount of reductant added via a respective DeNOx element is larger or smaller than a threshold value chosen according to the added amount of reductant the respective DeNOx element is marked as defective, wherein the NOx sensor is arranged downstream of the respective DeNOx element in the flow direction of exhaust gas to be passed through the exhaust gas aftertreatment system,
• d) testing a storage capacity for the reductant of the SCR catalysts, wherein if a change in measured values to be determined by a respective NOx sensor arranged downstream of the respective DeNOx element in the flow direction of exhaust gas to be passed through the exhaust gas aftertreatment system caused by an amount of reductant to be added via a DeNOx element of a respective SCR catalyst differs from a predetermined catalyst threshold value, the respective SCR catalyst is marked as defective, wherein the predetermined catalyst threshold value corresponds to a target storage capacity for the reductant of the SCR catalysts value and includes a temporal threshold value, wherein the change in the measured values occurs before a time duration associated with the temporal threshold value elapses, the respective SCR catalyst is marked as defective, wherein the temporal threshold value is a minimum time duration from a time point of addition of the reductant to the change in the measured values,
• and wherein the steps c) and d) are sequentially repeated for the components of the exhaust gas aftertreatment system correspondingly present in multiplicate.