A METHOD FOR TURNING OFF AN INTERNAL COMBUSTION ENGINE OF A VEHICLE POWERTRAIN SYSTEM AND A VEHICLE POWERTRAIN SYSTEM

A method for turning off an internal combustion engine of a vehicle powertrain system, wherein the powertrain system further comprises a transmission and a clutch arrangement connected to and arranged between the internal combustion engine and the transmission. The clutch arrangement comprises a first clutch arranged to couple the internal combustion engine to a first input shaft of the transmission and a second clutch arranged to couple the internal combustion engine to a second input shaft of the transmission. The first input shaft is drivingly connected to a first set of gears and the second input shaft is drivingly connected to a second set of gears. The first set of gears and the second set of gears are connected to an output shaft of the transmission. The method comprises the steps: controlling the internal combustion engine in an idling state when the vehicle is in a standstill position, wherein the first clutch and the second clutch are arranged in open positions; engaging the first input shaft with a first pre-selected gear of the first set of gears, and engaging the second input shaft with a second pre-selected gear of the second set of gears; initiating an engine turning off command; stopping the internal combustion engine by at least partly closing the first clutch and the second clutch for simultaneously introducing torque transfer to the first clutch and the second clutch into a transmission tie-up state for a controlled engine stop, wherein engine inertia of the internal combustion engine is captured in the first clutch and the second clutch.