Method and device for monitoring a pressure sensor

In an injection system having a pressure sensor determining a pressure in a pressure accumulator regulated by a pressure actuator, a device for monitoring the pressure sensor, the device comprising:

• an accumulator pressure evaluation unit for calculating an expected pressure value in a pressure accumulator for a given point in time based on a holding pressure preset at a pressure actuator and based on a detected rate of change in a mass balance of a medium contained in the pressure accumulator;
• and
• a comparator unit connected to said accumulator pressure evaluation unit comparing the expected pressure value calculated for the given point in time with a pressure value determined by a pressure sensor at the given point in time and detecting a malfunction in the pressure sensor if an absolute value of a difference between the expected pressure value and the pressure value determined by the pressure sensor exceeds a predetermined difference value said comparator unit further including a model pressure calculation unit calculating a gradient of the expected pressure value, a sensor pressure calculation unit for calculating a gradient of the pressure value determined by the pressure sensor, and a gradient difference unit connected to said model pressure calculation unit and to said sensor pressure calculation unit for calculating a gradient difference between the calculated gradients and for detecting a malfunction in the pressure sensor if an absolute value of the gradient difference between the calculated gradients exceeds a predetermined gradient difference value.