Method and device for diagnosing an ascertainment of a performance quantity of an internal combustion engine

A device for diagnosing an ascertainment of a performance quantity of an internal combustion engine, comprising:

• a comparing arrangement, which within the scope of a first diagnostic process, is used to compare a first value which is characteristic of a first performance quantity of the internal combustion engine at a first point in time after switching off the internal combustion engine to a predefined value;
• an error identification arrangement to identify an error when in the comparison it is detected that the absolute value of a first difference between the first value and the predefined value exceeds a predefined first threshold value for the first point in time;
• a specifying arrangement to specify the predefined first threshold value to be smaller the longer the time since the internal combustion engine has been switched off;
• and
• an error clearing arrangement to clear an identified error in a subsequent second diagnostic process when for a second difference between the first value and the predefined value for a second point in time it is detected within the scope of the subsequent second diagnostic process that the absolute value of the second difference does not exceed a second threshold value predefined for the second point in time, wherein the error clearing arrangement is configured so that within the scope of the subsequent second diagnostic process, the error identified within the scope of the first diagnostic process is cleared only when the predefined second threshold value does not exceed a predefined limiting value;
• a forming arrangement to form the predefined limiting value as a function of the predefined first threshold value.