A method for determining at least one rail pressure/closing current value pair for a pressure control valve of a common rail injection system of an internal combustion engine includes the following steps : operating the common rail injection system in an MU control mode; reducing the control current for the pressure control valve; detecting the pressure curve over time in the common rail and determining the rail pressure; determining the closing current based on the detected pressure curve; and associating the determined rail pressure and the determined closing current with a rail pressure/closing current value pair.