Emission Controls Operation

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 is closed with a solenoid valve. When engine is warm, solenoid valve is opened and EGR is allowed.
• AIR Management System - Control of this system is similar to that of the 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 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.
• Early Fuel Evaporation (EFE) System - The EFE system consists of a ceramic electric grid located under the throttle body. The EFE system improves air/fuel ratio control, improves fuel evaporation during cold operation, and improves idle speed quality. The ECM activates the EFE relay when MAT is less than 167°F (75°C), coolant temperature is less than 223°F (106°C), and battery voltage is greater than 10 volts. If any of these conditions are not met, the EFE relay is deactivated. If the EFE system is off when the vehicle is running, it will be re-activated when all 3 of the following conditions are met: MAT less than 100°F (38°C), coolant temperature less than 223°F (106°C), and battery voltage greater than 12 volts. The EFE system is activated for about 15 seconds when TPS position is greater than 30° and MAT is less than 140°F (60°C) to prevent icing of ceramic grid.