Microcomputer Control Unit

The MCU is located in the passenger compartment, behind right kick panel. The MCU monitors the CEC system data sensors, and, based upon mode of operation, generates an output control signal to the stepper motor mounted in carburetor. The MCU controls the following 2 modes of operation:

1. Open Loop. In this mode, the MCU determines the air/fuel mixture based upon engine operation rather than oxygen sensor input signals. The stepper motor is controlled by MCU to provide a pre-programmed amount of air for correct air/fuel mixture.
2. Closed Loop. When all input data and engine operation meet programmed criteria, the CEC system goes into closed loop operation. In this mode, oxygen sensor input signals are accepted by MCU to determine proper air/fuel mixture based upon oxygen content of exhaust gases. The MCU may also receive signals from the knock sensor and adjust ignition timing accordingly. Air injection is routed "downstream" or both "upstream" and "downstream" for various throttle positions.