Computer Command Control (C-3) System

The ECM is the control center of the C-3 system. Its function is to monitor input information from the various sensors, process this information, then generate output commands to the various systems that affect the performance of the vehicle.
The ability of the ECM to perform these functions is dependent upon a removable calibration unit called the PROM. There are specific ECM/PROM combinations for each vehicle and they should not be interchanged.
The ECM also performs the diagnostic function of the C-3 system, alerting the driver through a ``Check Engine'' light should any problem in the system arise and storing a code or series of codes which the technician uses as an aid in making repairs.