User:Corleco/GM Command Control Carburetor

The GM Computer Command Control System, or CCC is an engine management system created by General Motors, designed to control exhaust emissions. It was first implemented in 1981 model vehicles. Upon introduction, it was used by all U.S. market vehicles made by GM with the exception of trucks and diesel cars. At the base level, the system relied on a exhaust oxygen sensor, engine control module, and an electronically controlled carburetor in order to provide a 14.7:1 air/fuel ratio. However, CCC can handle up to 15 different inputs and control up to 9 different vehicle functions.

System overview
The ECM takes inputs from an oxygen sensor, coolant temperature sensor, throttle position sensor and engine speed sensor. Some applications also use a MAP sensor, vehicle speed sensor, knock sensor and/or EGR temperature sensor. Almost all of these sensors send analog signals, which are then converted to digital signals for processing by the ECM.

Upon starting, the ECM operates in open loop, sending signals to the carburetor that were pre-computed and held in memory by the battery when the ignition key is off. If the battery was disconnected, the ECM will resort to using nominal values for control that are permanently stored in memory. The decision to operate in open or closed loop is determined by the time since engine start, oxygen sensor readings, and coolant temperature.