NOTE: The Positive Crankcase Ventilation (PCV) system should be checked and cleaned at least every five years or 50,000 miles (80,000 km) on average. Inspection and service should be performed any time a malfunction is observed or suspected. Severe usage conditions may require shorter intervals — refer to the owner's manual for your truck.
To prevent combustion blow-by gasses from entering the atmosphere, all Mitsubishi gasoline engines use a closed type crankcase ventilation system. The system uses a PCV valve that is threaded into the valve cover. The PCV system supplies fresh air from the air cleaner through a metered orifice in the PCV valve to the crankcase. Inside the crankcase, fresh air is mixed with the blow-by gasses. This mixture passes through the PCV valve and into the air induction system.
The diesel engine does not use a PCV system; the crankcase vapors are instead routed through a breather hose and pipe where they are introduced into the intake airstream. After passing through the turbocharger, they enter the engine to be reburned.