General Motors has developed a computer controlled catalytic converter system. The C-4 system is the primary element in the GM effort to meet the twin goals of higher vehicle fuel economy and lower exhaust emissions. Major system components include a catalytic converter, electro-mechanical carburetor, exhaust oxygen sensor, coolant temperature sensor and electronic control module. The primary function of these components is to provide a precisely controlled air-fuel ratio to the catalytic converter for efficient reduction of regulated exhaust constituents.