Method for positive crankshaft ventilation diagnosis

A method for positive crankcase ventilation diagnosis in an engine system comprising an internal combustion engine, an intake duct connected to the engine, a PCV line connecting a crankcase of the engine with the intake duct and a sensor for determining an actual PCV pressure (pact) in the PCV line, the method comprising the steps of:

• performing a diagnosis measurement during a measurement period by repeatedly determining at least one input parameter (pint, ne, patm, Q), which is linked to the operation of the engine system, and the actual PCV pressure (pact), to obtain a plurality of data samples for a plurality of sample times (ts);
• using a prediction model (M) to determine a predicted PCV pressure (ppre) based on the determined at least one input parameter (pint, ne, patm, Q);
• and
• comparing the actual PCV pressure (pact) with the predicted PCV pressure (ppre) to diagnose the PCV line,
• wherein a diagnosis of the PCV line is based on a model error (perr), which is the difference between the predicted PCV pressure (ppre) and the actual PCV pressure (pact), wherein the model error (perr) being below a lower threshold (plt) is considered to indicate that the PCV line is intact, the model error (perr) being above an upper threshold (put) is considered to indicate that the PCV line is damaged, and the model error (perr) being between the lower threshold (plt) and the upper threshold (put) is considered as an inconclusive result.