Method for diagnosing a part of a powertrain system

A method for diagnosing a part of a powertrain system, said powertrain system comprising an internal combustion engine system having an internal combustion engine being a cam-less internal combustion engine provided with a plurality of cylinders, each cylinder being provided with an air inlet valve and an exhaust gas valve, said internal engine combustion system further comprising a fully variable valve actuation (VVA) system with individual valve actuation, said fully VVA system having a respective valve actuation arrangement for the air inlet valve and for the exhaust gas valve, said internal combustion engine system further comprising a control unit configured to control the valve actuation arrangement to operate the air inlet valve and the valve actuation arrangement to operate the exhaust gas valve, the method being executed as an on-board diagnostics routine by the control unit, and the method comprising the steps of:

• introducing disturbance injections in the form of air pulses into an air-path system by operating any one of the air inlet valve and the exhaust gas valve for any one of the cylinders to adjust a frequency and/or duration of air pulses during different load conditions of the internal combustion engine to add additional air pulses in the air path system of the powertrain system in addition to prevailing air pulses which are supplied in the air path system of the powertrain system for each respective load condition, wherein the frequency and/or duration of the air pulses is controlled by means of the fully VVA system;
• determining an operational behavior of the part of the powertrain system in response to the adjusted frequency and/or duration of the air pulses;
• and
• comparing the determined operational behavior of the part of the powertrain system with an expected behavior of the part of the powertrain system.