The ECU is an extremely reliable piece of hardware which has the capability to receive and process information hundreds of times per second. At the heart of the ECU is the microprocessor. It is the processing center of the ECU where input information is interpreted and output commands are issued. The process and output functions of the ECU can be divided into the following six areas:
• Fuel Injection Control
• ESA / VAST Spark Advance Control
• Idle Speed Control
• Self Diagnosis
• Related Engine and Emissions Control
• Failure Management (fail-safe and back-up)
Fuel, spark, and failure management functions will be covered individually in this chapter. Idle Speed Control, related engine systems, emissions control systems, and the self diagnosis system will be the subject of chapters 6, 7, 8, and 9, respectively.
ECU Power Distribution and EFI Main Relay Circuits
The ECU cannot properly function without dependable power feeds and ground circuits. The power distribution system involves several electrical circuits, protection devices, relays, and grounds.
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