Starting in January 2004, a closed crankcase ventilation system is used to meet new diesel emissions requirements.

Located in both valve rocker arm covers are diaphragms to control the venting of the crankcase gases. As the pressure of the crankcase gases increase, they overcome the spring holding the diaphragm in the closed position. If a vacuum situation arises in the crankcase, the diaphragm closes the port in the valve rocker arm cover. Closing the port will prevent unfiltered air to enter the crankcase.

The crankcase gases travel from the valve rocker arm covers through hoses to a tee, where they enter the turbocharger inlet duct. Because of the use of a closed crankcase ventilation system, it is normal for oil residue to be found on the turbocharger compressor wheel and inside the charge air cooler, pipes, and hoses.

No routine maintenance is required to the crankcase ventilation system.