Emission Control Systems: Description and Operation

Emission control systems are used to reduce harmful gasses (CO, HC, and NOx) released to the atmosphere. The emission control system consists of three major sub-systems.

1. CRANKCASE EMISSION CONTROL SYSTEM

The crankcase emission control system is a closed ventilation system that prevents blow-by gasses from escaping into the atmosphere. Blow-by gasses in the crankcase are routed back to the intake manifold for combustion.

2. EVAPORATIVE CONTROL SYSTEM

The evaporative emission control system prevents the escape of fuel vapors from the fuel tank and carburetor into the atmosphere. It consists of various components which collect and purge the fuel vapors to the intake manifold for combustion.

3. EXHAUST EMISSION CONTROL SYSTEM

The exhaust emission control system consists of a catalytic converter, exhaust gas recirculation, and air-injection or pulsair secondary air system.


One or more of the following emission control systems are used depending on the country, state, model, and engine. (The specific emission control systems used on your vehicle are listed under "SYSTEM I.D.").


AIR INJECTION (AI)
AIR SUCTION (AS)
DASH POT (DP)
EVAPORATIVE EMISSION CONTROL (EVAP)
EXHAUST GAS RECIRCULATION (EGR)
FUELPIPE RESTRICTOR (FR)
HIGH ALTITUDE COMPENSATION (HAC)
MIXTURE CONTROL (MC)
OXIDATION CATALYST (OC)
POSITIVE CRANKCASE VENTILATION (PCV)
THREE-WAY CATALYST (TWC)