Toyota 12204-28030 Valve Sub-Assy, Ventilation

The PCV valve and hose are located in the valve cover on all models except 2010 and later four-cylinder models. 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. The intake manifold must be removed to replace the PCV valve or hose. Disconnect the hose, unscrew the PCV valve from the cover, then reconnect the hose. With the engine idling at normal operating temperature, place your finger over the valve opening. If there's no vacuum at the valve, check for a plugged hose or valve. Replace any plugged or deteriorated hoses. Turn off the engine. Remove the PCV valve from the hose. Blow through the valve from the valve cover (cylinder head) end. If air will not pass through the valve in this direction, replace it with a new one. When purchasing a replacement PCV valve, make sure it's for your particular vehicle and engine size. Compare the old valve with the new one to make sure they're the same.

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.