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Reference.org
Engine control unit
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<p>An engine control unit (ECU), also called an engine control module (ECM), is a device that controls various subsystems of an <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engine</a>. Systems commonly controlled by an ECU include the <a href="/facts/Fuel_injection/0u4SxFyG">fuel injection</a> and <a href="/facts/Ignition_system/7Rqqltpr">ignition</a> systems. </p><p>The earliest ECUs (used by aircraft engines in the late 1930s) were mechanical-hydraulic units; however, most 21st-century ECUs operate using <a href="/facts/Digital_electronics/3kJcKbkw">digital electronics</a>. </p>