Normal Mode Crankcase Ventilation Function
WARNING: This page is about a different car, the 2018 Infiniti Q60. However, it is still accessible from the selected car via links, so may be relevant.
The partial load operation crankcase ventilation valve is usually open, and blow-by gas is sucked into the boost air distributor pipe from the oil separator.
During deceleration, the partial load operation crankcase ventilation valve is closed according to a signal from ECM. This stops blow-by gas flown from crankcase to intake air system and reduces noise.