Patent ID: 8312707

Claim:
A method for determining characteristic operating values of an exhaust-gas catalytic converter, the method comprising the step of: arranging a lambda sensor downstream of an exhaust-gas catalytic converter of an internal combustion engine with at least one cylinder and an exhaust-gas tract; receiving a measured signal from the lambda sensor; determining a first characteristic value that is representative of the NOx concentration as a function of the measured signal, wherein the first characteristic value for the NOx concentration is a NOx factor that is determined from a first characteristic curve as a function of the measured signal from the lambda sensor, the first characteristic curve being constant in sections of the first characteristic curve based on comparisons of the measured signal with one or more first predefined threshold values that are lower than a reference signal value; determining a second characteristic value that is representative of the HC concentration as a function of the measured signal, wherein the second characteristic value for the HC concentration is a HC factor that is determined from a second characteristic curve as a function of the measured signal from the lambda sensor, the second characteristic curve being constant in sections of the second characteristic curve based on comparisons of the measured signal with one or more second predefined threshold values that are higher than the reference signal value; and detecting a fault condition of the catalytic converter based on at least one of the NOx factor and the HC factor.