Microprocessor Control Unit (MCU)
The MCU is a solid-state micro-computer located on the left fender panel. It is the "brain" of the system and receives inputs and sends signals -through a 24-pin connector. The MCU is capable of operating in 3 modes: Initialization, Open loop and Closed loop.
Initialization mode occurs when the engine is started. In this mode the MCU richens the fuel mixture for easy starting. Open loop operation is controlled by MCU programming. Air/fuel ratio is fixed at a pre-determined level and allows good driveability at idle, moderate-to-heavy acceleration, and deceleration.
Closed loop operation occurs when the engine is warm and vehicle is operated at light load conditions. In closed loop, the MCU controls the air/fuel mixture in response to signals from an oxygen sensor in the exhaust manifold.