Engine Management (Computer) Systems

How do they work?

Various sensors monitor the engine. Each sensor produces an electrical signal, and the signal changes as the condition being monitored changes. The electrical signals are sent to an electronic control unit, which contains a microprocessor and a memory. the microprocessor processes all the information from the sensors and, by referring to its memory, can tell exactly what conditions the engine is running under. The control unit is able to “look up” values stored in its memory, and decide how much fuel the engine needs, and what the ignition timing (petrol engines) or injection timing (diesel engines) should be at that particular instant. The control unit also controls the engine idle speed and the emission control systems.

On-board diagnostics

Engine management systems usually have an-onboard diagnostic system (or self-diagnostic system) which is used to store details of any problems. If a component is faulty, the system stores a trouble code in the control unit. The trouble code can be read using a trouble code reader, or sometimes a diagnostic light on the dash, to indicate which component is faulty. This allows problems to be traced quickly and easily.