GM Micro-Computer Engine Control System

The General Motors microprocessor based Computer Controlled Catalytic Converter (C-4) system used on 1980 California vehicles and nationwide in 1981 is presented. The basic system function is to maintain engine exhaust air-fuel ratio control so that oxidation and reduction characteristics of three-way catalytic converters can be effectively utilized. Control strategies and components used in the Closed Loop Carburetor Control (CLCC) function are reviewed. Other system components and functions including secondary air management control, electronic spark timing, idle speed control, torque converter clutch control, controlled canister purge, exhaust gas recirculation control, early fuel evaporative control and system self diagnostics are presented.