Engine Management System

Engine Management System (EMS)

Engine Management System (EMS) -

EMS stands for Engine Management System which consists of a wide range of electronic and electrical components comprising of sensors, relays, actuators and an Engine Control Unit. In addition, they work together to provide the Engine Management System with vital data parameters that are essential to govern the various engine functions effectively. The Engine Management system is incorporated in the modern day engine technologies, such as MPFi & GDi systems in Petrol engines and CRDi system in diesel engines for improved performance.


ECU stands for Engine Control Unit and ECM for Engine Control Module, both are the same. ECU/ECM is also the generic term which refers to any Electronic Control Unit / Module respectively.

ECU, Engine Management System
ECU (Photo: Courtesy Bosch)

Engine Control Unit -

The Engine Control Unit is a central part of the Engine Management System which is virtually the 'Brain' of an engine. It plays an important role of collecting, processing, analyzing and executing the data it receives from various sub-systems. Furthermore, an ECU comprises of a computer which uses a microchip to process the inputs from various engine sensors in real-time.

ECU & Engine Management System
Input & Output of an ECU, Engine Management System

The Electronic Control Unit contains hardware and software. The printed circuit board (PCB) of the ECU consists of a micro-controller chip or the CPU (Central Processing Unit). The software is stored in this micro-controller or other chips on the PCB. An ECU can be re-programmed by updating the software or by replacing chips. All the engine sensors send data inputs by the way of electrical signals to the ECU which, in-turn, controls various actuators, ignition timing, variable valve timing etc.

How an ECU Works?

Based on this data input, the ECU precisely calculates and delivers the ideal air-fuel mixture. It also regulates the idle speed of the engine and limits the top speed of a vehicle. This system is also widely referred to as an ‘Electronic Engine Management System’ or the EMS. Furthermore, the modern day ECUs can be customized to suit different vehicular applications and varying customer demands. In addition, some cars have an individual ‘Control Module’ for the every major system. A modern car may contain the following individual Control Modules which control the respective systems.

Control Modules, Engine Management System
Various Control Modules in a car

An Engine Control Unit connects to all the individual Electronic Control Modules (ECMs). A modern day car consists of more than one Control Modules; each exclusive for every major system which improves the performance. The manufacturers seldom refer to these systems as car's computers since these are multiple computers as opposed to single one.

Engine Management System
A diagram showing various control modules in a modern day car


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