Computers and Control Systems: Description and Operation

The computerized engine control system is built around an Micro Computer Unit (MCU). The MCU monitors various engine operating conditions. Based on these conditions, the MCU determines the proper mode of operation. There are two modes of operation, OPEN LOOP and CLOSED LOOP. During open loop operation, the air-fuel ratio is predetermined by the MCU for several engine operating conditions, such as:
^ start-up
^ cold engine operation
^ wide open throttle operation (WOT)

During closed loop operation the MCU generates output signals to provide the proper air-fuel mixture, proper ignition timing and engine idle speed.


MCU INPUTS MCU OUTPUTS

^ Coolant Temperature Switch ^ Stepper Motor
^ Thermal Electric Switch ^ Idle Relay
^ Four- and Ten-Inch Hg Vacuum Switch ^ Sole-Vac Throttle Positioner
^ Oxygen Sensor ^ Upstream and Downstream Solenoids
^ Wide Open Throttle (WOT) Switch ^ PCV Solenoid
^ Knock Sensor
^ Distributor