Under the hood, center, upper engine area, mounted in PCV hose, located between the crankcase breather chamber and intake manifold.
A crankcase ventilation system is a way for gases to escape in a controlled manner from the crankcase. A common type of such system is a positive crankcase ventilation (PCV) system, the heart of which is a PCV valve—a variable-restriction valve that can react to changing pressure values and intermittently allow the passage of the gases to their intended destination (which nowadays is the engine's intake stream).