If the measured value has dropped by more than 0.5 bar

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 BMW 328xi, 2012 BMW 328i, 2011 BMW 328xi, 2011 BMW 328i, and 2010 BMW 328xi. However, it is still accessible from the selected car via links, so may be relevant.

Start engine and wait briefly for a stable pressure increase.
Switch off the engine and immediately pinch off the delivery line just before the pressure gauge with the special tool 13 3 010.
Note down measured value
Read off measured value again after approx. 20 to 30 minutes while engine is stopped