Emission Control Systems - General Information, Crankcase Ventilation System

General Information

All Toyota vehicles are generally equipped with the following emission control systems:

Crankcase Ventilation; Catalytic Converter; Evaporative Emission Control; Exhaust Gas Recirculation (3S-FE engines only).

The systems operate as follows.

Crankcase Ventilation System

To reduce the emission of carbon monoxide (CO) from the crankcase into the atmosphere, the engine is sealed, and blow-by gases and oil vapor that enter the crankcase are DRAWN from the crankcase through the positive crankcase ventilation (PCV) valve into the intake manifold, where they mix with the air-fuel mixture and are burned in the engine cylinders.

At high intake manifold vacuum, gases are drawn well out of the crankcase. At low vacuum, gases are forced out of the crankcase by relatively higher pressure. If the engine is worn, increased crankcase pressure (due to increased blow-by) will force gases back into the engine intake regardless of manifold condition.