Scion 12204-28030 Valve Sub-Assy, Ventilation

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The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors. It circulates fresh air from the air cleaner through the crankcase, mixing it with blow-by gases. The mixture is rerouted through a PCV valve to the intake manifold. The PCV valve restricts flow when intake manifold vacuum is high, maintaining idle quality. In abnormal conditions, excessive blow-by gases flow back through the crankcase vent tube into the air cleaner for normal combustion. The PCV system consists of the PCV valve, blow-by filter, and vacuum hoses connecting these components to the engine. Regularly checking and replacing the PCV valve is important.

On 2010 and later four-cylinder models, the PCV valve and hose are located on the back side of the engine underneath the intake manifold.

When purchasing a replacement PCV valve, make sure it is for your particular vehicle and engine size. Compare the old valve with the new one to ensure they are the same.