Engine control unit in a brief

Published: 14th June 2010
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The main purpose of the Engine Control Unit (ECU) is to control the various features of the internal combustion during the operation of the engine, and in the advanced types of engines, The ECU monitors the engine by using sensors that fitted with in the engine like MAP sensor, throttle position sensor, air temperature sensor, oxygen sensor, knock sensor, and many more. The Sensors can gather information about the cars quantity of fuel, ignition timing and other parameters. These sensors will give the input data to the ECU and the engine's ECU will works according to it.

These sensors monitor various aspects such as the ambient air temperature, engine/coolant temperature, exhaust /manifold temperature; exhaust O2 content, throttle position, the rpm of the engine, the vehicle road speed and crankshaft position.

Engine Control Unit (ECU) will deliver the required commands to the actuators like spark plugs and fuel injectors and fuel pump and other actuators.

The ECU (Engine Control Unit) uses the closed -loop Feedback control method, where it monitors the output of a system in order to control the inputs to a system.

The ECU (Engine Control Unit) performs calculations every second, by the bases of the programmed interpretation of all the available input data.

The ECU will always keep tracking the engine's sensors and actuators to bring out a satisfactory performance of the car's engine.

And there is a learning process that the ECU used to track the tolerance changes of the sensors and actuators on the engine, and store it in a RAM in the ECU, like the change in the values of fuel injector pulses according to the engine load, to use these data to improve the engine performance.

We have a process called Reset ECU and it means to clear all the long term memory learned values back to the default values and the ECU will start the learning process again, this action can be done by a Scan tool for two reasons:

1. To clear the Fault code memory after fixing the problem that caused the error.

2. The other is to reset the spark advance trim value. The advance trim controls how much the timing is retarded from what the factory engineers considered optimum.

The engine may run rough or idle poorly right after ECU reset. The ECU now has default numbers in its trim memory - it has to adjust them to match the tune of your engine and its sensors and actuators. It might take a day or two of driving in traffic before the engine will settle down again.


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