All current BMW engines incorporate a pressure-controlled crankcase ventilation system. The crankcase ventilation systems use various different crankcase ventilation valves, depending on the engine type. Although the valves all look different, they function similarly, using a spring and diaphragm assembly to control the crankcase pressure. A properly functioning pressure control valve is designed to maintain a slight vacuum in the crankcase, which assures reliable crankcase venting during all engine operating conditions. A malfunctioning crankcase ventilation valve may cause the following complaints: Engine runs roughly, Whistling noise from the crankcase ventilation valve, Check engine light on – possible DME faults stored: misfire all cylinders, oxygen sensor/mixture adaptation faults, etc. DME faults stored in the memory will vary, depending on the DME version and the effect of the crankcase pressure for example mixture adaptation faults, trim faults, etc.