What Should You Know About Engine Control Unit (ECU)?

If you compare the engine of your car with a human body, then the piston would be the heart, the headlight could be the eyes, and the ECU or engine control unit could be the brain. In general, the ECU makes sure everything in the engine are running effectively and smoothly.

In this article, we will show you the elements of an ECU, the elements of the motor that an ECU controls and some methods to troubleshoot the ECU, which could be found in any car dealers or auto stores.

Car engine control unit (ECU) isolated on white background


The Elements of The Motor That an ECU Controls​

The ECU or the computer of a car helps to control a wide range of systems in the motor. The following parts will show you the information on those systems such as ratio of fuel and air, timing of ignition and idle pace.

Ratio of Fuel and Air​

Most of latest motors use some kinds of gas injection to make sure that the ratio of fuel and air is suitable. In general, the ECU would decide the amount of gas to put depending on a couple of sensor measurements.

The position of a throttle sensor shows the level of pressing of a throttle pedal. The sensor of mass flow calculates the amount of extra air coming to the motor. The sensor of motor cooling temperature indicates if the motor is warming up. Extra gas would be supplied if the motor is still cool.

Timing of Ignition

Inside a sparking ignition motor, a spark is needed to kick off the combustion in a combustion section. The precise timing of a spark could be changed by an ECU to make sure it improves the economy and power.

Knocks, which is a destructive condition for the motors, could be noticed by an ECU and solved by holding up the timing of a spark to keep the timing of ignition from getting early compared to the stroke of compression.

Idle Pace

A position of a crankshaft sensor could send the information to an ECU in terms of idle pace. This sensor plays a key role in performance of the motor timing such as timing of valve, sparking event, injection of gas.

An automatic stop of throttle is often used for controlling the idle pace. The controlling of idle pace has to anticipate the load of the motor on idle.

The differences in load could be made by the heating system, the energy brake, the steering system or the AC. In addition, other things that could have effects on the idle pace and load of engine include status of transmission, temperature of the engine or the duration and life of the camshaft.

Changing Timing of Valve

In a wide range of motors, an ECU would control the cycle of motor while the valve is opening. At lower paces, the valve is opened later than at higher paces.

When the valve is opening at a higher pace, the car could optimize the flow of air to a cylinder. As a result, it helps to increase the economy and power of a motor.

How to Troubleshoot an ECU?

In many aspects, solving a problem in ECU is quite similar to tackling an issue in a personal computer. There might be elements that a typical user could change, but the best option is to change the whole computer.

You need to have specific devices and practical knowledge to take apart and fix an ECU.

TOYOTA Engine and Power Control Unit

Signs of a Badly Operating ECU

​There are a couple of factors for to notice that might be a symptoms of an inappropriately running ECU. First, your vehicle might not start or if it would run with improperly stalling or idling.

As the ECU plays the most important role in controlling the dash error light, this light might not be working suitably. If an owner thinks that this unit might be broken, there are a lot of ways to check before changing to another ECU.

In general, the gas pump, the sparking plug and the alternator could be checked for damage, which leads to the problems in an ECU of your car.

Remove an ECU​

In general, an ECU is placed in various positions in different models and brands of car, but you could use following useful tips to remove an ECU for examining.

First, you need to unplug the terminals of battery before any electric tasks is done on your vehicle. In a couple of models, you could find the ECU in the console place next to a firewall of the motor section in your car.

For other versions, you could find this unit under a carpet. After taking this carpet, you should remove a protective plate and 2 plugs of an ECU.

In addition, always remember to read the manual guide of the car to decide the exact position of the ECU and the best way to get it.


To sum up, ECU is probably one of the most important advancement in automobile industry. By making use of latest technology in computer, car producers have been able to offer improved accuracy of the engine.

Those advancement have made vehicle to save more fuel.

This article has provided an insight in the methods a vehicle’s computer operates to control the engine’s performance.​


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