Patent ID: 8347700

Claim:
A device for operating an internal combustion engine which has a plurality of cylinders, each of these being assigned an injection valve, and an exhaust-gas train comprising an exhaust-gas catalytic converter and a lambda probe that is arranged in the exhaust-gas catalytic converter or upstream thereof, comprising: an assignment unit which is configured to determine cylinder-specific lambda signals as a function of the measured signal of the lambda probe and to determine, as a function of the cylinder-specific lambda signals, lambda deviation signals for the respective cylinders relative to a lambda signal that is averaged over the cylinder-specific lambda signals, an observer comprising a sensor model of the lambda probe, said model being arranged in a feedback branch of the observer, wherein the observer is configured such that the cylinder-specific lambda deviation signals are supplied to its input side, and observer output variables relating to the respective cylinder are representative of deviations of the injection characteristics of the injection valve of the respective cylinder from predefined injection characteristics, and a parameter detection unit, which is configured to impose a predefined disturbance pattern (PAT) from cylinder-specific mixture deviations, modify at least one parameter of the sensor model as a detection parameter, in response to the respectively predefined disturbance pattern, until at least one of the observer output variables represents that portion of the disturbance pattern which is assigned to its cylinder, and output the at least one detection parameter.