A METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE SYSTEM

The invention relates to a method for operating an internal combustion engine system (), wherein the internal combustion engine system () is provided with an air intake duct (), an exhaust gas duct () and an exhaust gas recirculation (EGR) system (), wherein the EGR system () comprises an EGR conduit () that fluidly connects the exhaust duct () and the intake duct (), and wherein a gas feeding device () configured to feed exhaust gas from the exhaust duct () to the intake duct () is arranged in the EGR conduit (). The method is characterized in that it comprises the step of: detecting an indication of accumulated deposits of soot, hydrocarbons or other contaminants in the gas feeding device () by determining whether a rotational friction of a rotary member () of the gas feeding device () exceeds a threshold value. The invention also relates to an internal combustion engine system () configured for being operated by such a method and to a vehicle () provided with such an engine system (). The invention further relates to means for controlling the above method.