The Positive Crankcase Ventilation (PCV) system removes harmful gases from the crankcase before damage occurs. It uses intake manifold vacuum to draw crankcase vapors back into the intake manifold to be burned. Toyota uses either a fixed orifice or variable flow PCV valve system. The variable flow system more accurately matches the ventilation flow to the blowby production, optimizing crankcase ventilation performance. It consists of a PCV valve, purge hose, and breather hose. The PCV valve regulates blowby flow into the intake manifold based on engine load. Problems with the PCV system can disrupt the air/fuel ratio and cause oil consumption or contamination.