control method of the position of a solenoid valve using dithering ; the control method provides the steps of : determining a target current across the solenoid valve which is expressed in digital form with a given minimum quantization interval ; adding a dithering square wave to the target current ; controlling the voltage applied to the solenoid valve to cause the current across the solenoid valve to track the target current added to the dithering square wave ; jiggling the dithering square wave with a frequency which is a sub - multiple with respect to the maximum variation frequency of the current across the solenoid valve ; and varying the amplitude of the dithering square wave for a fraction of the period of the dithering square wave itself and by an amount equal to the minimum quantization interval for temporarily determining a deviation of the mean value of the dithering square wave with respect to zero and therefore obtaining a corresponding variation of the mean value of the target current .