System and method for diagnosing a crankcase ventilation system of an internal combustion engine

A method for diagnosing a crankcase ventilation system of an internal combustion engine comprising a system for diagnosis, the system comprising an internal combustion engine with at least one combustion chamber and being designed as an internal combustion engine turbocharged via an exhaust gas turbocharger, the combustion chamber being bounded by a cylinder head, a cylinder in an engine block, and a piston that is connected via a connecting rod to a crankshaft that is disposed in a crankcase;

• an air supply system for feeding fresh air into the combustion chamber of the internal combustion engine;
• at least one aeration line connecting the air supply system to the crankcase;
• at least one vent line, which is different from the at least one aeration line and connects the crankcase to the air supply system;
• and a pressure sensor disposed in the crankcase or the at least one aeration line, the method comprising:
• operating the internal combustion engine at an operating point at which a boost pressure is built up by a compressor of the exhaust gas turbocharger;
• and
• evaluating a change in a pressure in the crankcase or in the at least one aeration line downstream of a throttle in response to the boost pressure build-up,
• wherein, when the boost pressure builds up above a threshold value, starting from a substantially constant vacuum in the crankcase, a pressure maximum and a subsequent pressure minimum of the pressure in the crankcase or in the at least one aeration line downstream of the throttle are determined and a functioning of the crankcase ventilation system is deduced from the pressure difference between the maximum pressure and the minimum pressure.