A method for identifying deviations in quantity in the case of a fluidic metering system (100-165), in particular an internal combustion engine of a motor vehicle, in which at least one conveying pump (125) for conveying a fluid, and at least one pressure sensor (135) for determining a fluidic pressure in the metering system (100-165), are disposed, wherein it is provided in particular that a test admeasurement of fluid is carried out (205), that a temporal pressure drop in the metering system (100-165) is detected (210), that the detected temporal pressure drop is compared with a pressure drop (215) that is to be theoretically expected (220), and that a deviation in quantity of the metering system (100-165) is determined by means of the result of the comparison (225).