EMISSION SYSTEM
Several systems are used to control emission of pollutants. System usage depends on model, engine and transmission combination. Each system is designed to control a particular vehicle emission.
Note. There are 2 light duty truck emission control standard classifications: Light Duty and Heavy Duty. Light Duty refers to vehicles up through 8500 lbs. GVW; Heavy Duty refers to vehicles over 8500 lbs. GVW.
AIR INJECTION REACTOR (AIR) OPERATION
This system uses air pump to supply additional fresh air to exhaust ports, further burning exhaust gases before they reach exhaust system. This reduces hydrocarbon (HC) and carbon monoxide (CO) emissions.
AIR MANAGEMENT SYSTEM OPERATION
This system provides additional oxygen to exhaust gases to continue combustion process. System is used on all engines except 2.5L. For further information, refer to CEC INTRO & TROUBLE SHOOTING article or appropriate TESTING article in the COMPUTER ENG CONTROL section.
CATALYTIC CONVERTER (CAT) OPERATION
Used on all Light Duty emission models, this unit is connected into exhaust system so exhaust gas passes through converter. Inside converter, a chemical reaction takes place which reduces exhaust emissions.
COMPUTER COMMAND CONTROL (CCC) OPERATION
CCC is an electronically controlled exhaust emission system. It monitors several engine/vehicle functions and controls various operations, including automatic transmission torque converter clutch (TCC), downshift control and manual transmission shift light. CCC system aids in control of exhaust emissions while maintaining good fuel economy and driveability.
EVAPORATIVE EMISSION CONTROL (EEC) OPERATION
This system, used on all except Federal Heavy Duty emissions models, is designed to keep fuel system vapors from escaping to atmosphere. This sealed system separates fuel vapors and routes them to engine to be burned, while retaining liquid fuel in tank. Carbon canister stores vapors until engine draws them off for burning.
FUEL CONTROL OPERATION
Used on all models, ECM controls air/fuel delivery to combustion chamber by controlling injector fuel flow. ECM controls idle speed and fuel pump (in tank).
ELECTRONIC SPARK TIMING & ELECTRONIC SPARK CONTROL OPERATION
On electronic spark timing ECM controls ignition timing. Electronic spark timing (EST) is used on all engines. Electronic spark control (ESC) uses a knock sensor along with ECM to control spark timing by allowing engine maximum spark advance without spark knock. ESC system is used on all engines except 2.5L and 7.4L. For further information, refer to CEC INTRO & TROUBLE SHOOTING article or appropriate TESTING article in the COMPUTER ENG CONTROL section.
OTHER EMISSION SYSTEMS
For additional information on description, operation, testing and adjusting other exhaust emission systems, refer to CEC INTRO & TROUBLE SHOOTING article or appropriate TESTING article in the COMPUTER ENG CONTROL section.
COMPONENT TESTING
Note. Testing information not available.