Emissions Control

The ECM controls operation of EGR system, AIR management system and canister purge control operation. The ECM also controls Early Fuel Evaporation (EFE) system. Description of each system is as follows:

• EGR System
  
  Signals received from coolant sensor provide ECM with engine temperature. When engine is cold, ported vacuum to EGR valve is closed with a solenoid valve. When engine is warm, solenoid valve is open and EGR is allowed.
• AIR Management System
  
  Control of this system is similar to that of EGR system. When engine is cold, ECM energizes an air control solenoid which allows air to flow to air switching valve. Switching valve is energized by ECM to direct air to exhaust ports to aid in quickly heating oxygen sensor to 600°F (316°C). When engine is warm or in closed loop operation, ECM de-energizes air switching valve and air is sent directly to catalytic converter to assist in oxidation of HC and CO. If the air control valve detects a rapid increase in manifold vacuum (deceleration), if certain operating modes exist or if ECM detects any failure in the system, air is diverted to air cleaner or dumped to atmosphere.
• Canister Purge Control Operation
  
  Vacuum to canister purge control valve is controlled by ECM with a solenoid valve. When engine is idling or in open loop operation, solenoid valve is energized and vacuum is blocked to purge valve. When system is in closed loop operation, solenoid valve is de-energized and vacuum can be applied to purge valve to draw collected vapors into intake manifold.
• Catalytic Converter
  
  A catalytic converter is used on all vehicles to reduce emissions levels of the 3 major pollutants. These are: Hydrocarbons, Carbon Monoxide and Oxides of Nitrogen (NOx). There are 2 converter designs used, the pellet-type on all California models and the monolithic honeycomb design on all others. The converter medium, whether pellets or ceramic monolithic, is coated with Platinum, Palladium and Rhodium. When exhaust gases come in contact with these metals, HC and CO are oxidized (burned) and NOx is reduced to its basic elements, further reducing total engine emission levels.