Disclosed is a method for operating a forming device for forming plastics material preforms into plastics material containers, wherein the forming device has a movable carrier on which a plurality of forming stations are arranged, wherein each of these forming stations forms plastics material preforms into the plastics material containers by applying a flowable and, in particular, gaseous medium in an operation mode, wherein in the operation mode at least two different pressure levels are applied to the plastics material preforms for the expansion thereof and at least two valves are used for this application, wherein at least one measured value is determined, at least at times, which is characteristic of a switching time and/or a switching time delay of at least one of the valves, wherein this measured value results from a pressure measured value.