Fourier Diagnosis of a Charge Cycle Behavior of an Internal Combustion Engine

A diagnostic tool diagnoses a charge cycle behavior of an internal combustion engine with a plurality of cylinders. The diagnostic tool ascertains a rotational speed profile of the internal combustion engine. From the determined rotational speed curve, the diagnostic tool ascertains a peculiarity of at least one charge exchange characteristic variable by performing a Fourier transform. The diagnostic tool assigns a deviation type to the rotational speed profile as a function of the ascertained peculiarity of the charge exchange characteristic variable.