Patent ID: 8839612

Claim:
A method for operating an exhaust system of an internal combustion engine, the method comprising reducing oxide (NO x ) by a SCR catalytic converter; and monitoring, by a control device, an ageing state of the SCR catalytic converter, wherein, during a temporally limited phase having a ratio of nitrogen dioxide to nitrogen oxide less than one in an exhaust gas, a conversion of the SCR catalytic converter is acquired and evaluated and the ageing state of the SCR catalytic converter is determined therefrom, wherein the functional capability of a catalytically coated, oxidizing exhaust gas after-treatment component is diagnosed, and wherein a first NO x desorption peak, which has a large NO 2 /NO x ratio, is generated with a first lambda value >1 and the conversion of the SCR catalytic converter is determined therewith, in that a NO x desorption peak having a smaller NO 2 /NO x ratio is generated with a second lambda value and the conversion of said SCR catalytic converter is determined therewith, in that the two conversions of said SCR catalytic converter ascertained using NO 2 /NO x ratios which vary in size are compared and in that the functional capability of the oxidizing coating of the upstream exhaust gas after-treatment component is recognized/detected by means of the evaluation of the conversions of the SCR catalytic converter.