Abstract: In a method for detecting the opening of a passive pressure limiting valve for releasing fuel from a common rail fuel injection system to a tank with a fuel supply including a throttle wherein, based on a stationary rail pressure present during manual operation, a load reduction is detected when the rail pressure exceeds a first limit value and, as a result, a PWM signal for controlling the suction throttle is temporarily increased, the opening of the pressure limiting valve is recognized if, as a result, the rail pressure exceeds a second limit value and increases still further.