METHOD FOR DIAGNOSING AN EXHAUST GAS CATALYTIC CONVERTER, DIAGNOSIS DEVICE AND MOTOR VEHICLE HAVING SUCH A DEVICE

A method for diagnosing an exhaust-gas catalytic converter (28) arranged in an exhaust-gas system (20) of an internal combustion engine (12) for the catalytic conversion of at least one exhaust-gas component from the internal combustion engine (12), which has an exhaust-gas recirculation means with which a partial stream of the exhaust gas can be drawn off downstream of the catalytic converter (14) and fed into the combustion air of the internal combustion engine (12), involves determining the current raw emission (NOx-raw) of the internal combustion engine (12) in of the exhaust-gas component; measuring the current concentration of the exhaust-gas component (NOx-meas) in the exhaust gas upstream of the catalytic converter (28); and determining a diagnostic value for the catalytic converter (28) in terms of the conversion of the exhaust-gas component as a function of the modelled raw emission (NOx-raw) from the internal combustion engine (12) and the measured concentration of the exhaust-gas component (NOx-meas). The invention further relates to a diagnostic device configured to perform the method and a motor vehicle having such a device.