DriveMaster® - Lesson 3: Electrical Control Systems (ECM), © 2001 Horton, Inc.

	LESSON 3: ELECTRICAL CONTROL SYSTEMS (ECM)

	3.1 Electronic Control Module		INDEX
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	The electrical wiring that controls the fan drive varies from one vehicle to another, but generally will be one of three types of systems: ECM controlled Normally-Open Normally-Closed Engine manufacturers include Electronic Control Modules (ECMs) in their new designs to control the engine, transmission, and other critical operations to improve engine performance, reliability, and fuel efficiency. An ECM is essentially a digital computer, containing a microprocessor, random-access-memory (RAM), and read-only-memory (ROM). The ROM contains the computer's program. Design engineers can change a vehicle's control system and engine performance simply by changing the ECM's computer program. Electronic Control Modules are simpler and more reliable than independent hard-wired systems. The decision logic is in the computer program and not the wiring, and all sensors and actuators are wired to the ECM instead of to each other.		Learning Objectives: • Describe the function of an ECM. • State the advantages of an ECM system over an independent, hard-wired control system. NOTE: An ECM is essentially a digital computer, used to control the engine, transmission, and other critical operations to improve performance reliability, and efficiency.

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