Emission Controls

The ECM controls operation of EGR system, AIR management system and canister purge control operation. See Figure . Description of each system is as follows:

• EGR System  Signals received from coolant sensor provide ECM with engine temperature data. 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.