Monitoring the ventilation of a crankcase of an internal combustion engine

An internal combustion engine comprising:

• a combustion chamber with a reciprocating piston inside a cylinder;
• a crankcase in which the piston is arranged at least in part and fluidically connected to the combustion chamber by a gap between the piston and the cylinder;
• an exhaust system fluidically connected to the combustion chamber;
• a nitrogen oxide sensor to arranged in the exhaust system and configured to detect an amount of nitrogen oxide in exhaust gas of the internal combustion engine;
• and
• a control unit configured to
• determine a predefined operating mode of the internal combustion engine defined by substantially no combustion of an air/fuel mixture taking place inside the combustion chambers;
• determine an amount of nitrogen oxide in the exhaust gas during the predefined operating mode of the internal combustion engine using the exhaust gas sensor;
• and
• identify functional ventilation of the crankcase if the detected nitrogen oxide level exceeds a predefined nitrogen oxide threshold or identifying a malfunction if the detected nitrogen oxide level is below the predefined nitrogen oxide threshold.