Patent ID: 7849844

Claim:
A method for operating an internal combustion engine with an exhaust gas catalytic converter, first exhaust gas probe, which is arranged so that it can be used in a lambda control, and a second exhaust gas probe, which is arranged so that it can be used in a trim control, the method comprising the steps of determining an HC quality value, which is representative of an oxygen storage capacity of the exhaust gas catalytic converter as a function of a measuring signal from the second exhaust gas probe, determining a NOx correction value as a function of the measuring signal from the second exhaust gas probe, as a function of signal elements, which are representative of residual oxygen present, determining a NOx quality value as a function of the HC quality value and the NOx correction value, determining a lambda quality value as a function of an actual value and a base setpoint value of the air/fuel ratio, which is representative of a temporal profile of a deviation of the actual value from the base setpoint value of the air/fuel ratio, determining an error indicator as a function of the lambda quality value and the NOx quality value, which in a first value range is representative of a mixture component error and in a second value range is representative of an exhaust gas catalytic converter error, adjusting at least one of a controller parameter of a trim controller and a trim setpoint value of the trim controller as a function of the NOx correction value if the error indicator is representative of the mixture component error and the error indicator is only deemed to be valid in respect of the mixture component error if the error indicator continues to be representative of mixture component error despite the adjustment.