Computers and Control Systems: Description and Operation

These vehicles are equipped with a Programmed Fuel Injection Electronic Control Unit (ECU). The ECU controls all phases of engine operation. In order to accomplish this control, the ECU relies on the input from a variety of engine operation sensors. It then compares these input signals with those stored in memory to determine what steps should be taken to achieve maximum performance, fuel economy, and meet all emission control standards. The ECU then outputs the necessary signals to the fuel system, ignition system, air control system, and the emission control systems. The ECU also records any malfunctions in the monitored systems. When a malfunction is detected, the ECU will insert a pre-programmed value to substitute for the defective signal, flash the Check Engine light, and store the malfunction in erasable memory as a numeric code. Additionally, should the ECU itself fail, their is a back-up circuit which will control the fuel system to allow the vehicle to continue functioning (Back-up Mode).