Check Engine light turns on: what is the cause?

If one day, you notice the check engine light is on on your car dashboard and you don’t understand why it is on. So don’t worry yet, it could come from the gas tank cap being open or your engine oil cap not being tightly closed.

But if you have checked and closed the engine oil cap, fuel tank, and engine oil gauge and the engine error light is still on, maybe even flashing, then you should start to worry, because this is the case. is a sign that your car is experiencing damage.

Below, CarOn will list with you some reasons why the check engine light comes on in your car that you can refer to to identify and fix these errors as soon as possible.

What is the Check Engine light?

Check Engine – the engine warning light is an extremely important detail of every vehicle. According to experts, the Check-Engine light must be turned off after starting or operating the vehicle, under normal engine conditions. Check-Engine light error occurs when this light remains on after the vehicle is in operation (so it is also called “goldfish error”).

When the “yellow” light is on, it means there is an improper signal from the engine sensor system that tells the ECU box to activate the light on the dashboard, which helps your car detect problems that the car has. are encountering.

Causes of the Check Engine light coming on

Spark plug

The ignition system, electrical wires and spark plugs are closely related to the fuel combustion process. If one of these parts is damaged, it will cause the engine to operate weakly. This is also one of the common reasons why the car has a goldfish error.

caron brown brick red spark plug

Ignition coil

The car ignition coil is responsible for creating high-voltage current so that the spark plug emits an electric spark that ignites the gas and fuel mixture in the engine cylinder. If the ignition coil malfunctions, it will affect the spark plug. Seriously, the spark plug may not be able to ignite, leading to the engine stalling. Therefore, when the vehicle’s ignition coil fails, the Check Engine light will usually light up yellow.

You can also learn more about the signs that the ignition coil is having problems through the article below

Fuel injectors

Fuel injectors after a long time of operation can become clogged due to dirt in the gasoline. If your fuel tank contains a lot of dirt and you don’t replace the fuel filter regularly, dirt in the fuel can clog the injectors and affect the engine’s performance. In addition, if you frequently drive until the low fuel level light comes on, it will also increase dirt in the tank, leading to the check engine light coming on.


Fuel tank cap

It sounds simple, but if your fuel tank cap is not tightly closed, the engine error light will illuminate. This is also the first thing you should check when you see the check engine light come on to avoid wasting time checking for other common errors while the simplest details are being overlooked.

Gas vapor control system (EVAP)

The gasoline vapor control system is located on the gasoline pipeline to help recover and process gasoline vapor, helping to reduce environmental pollution. When this system is damaged, the check engine light also lights up. When this system is damaged, gasoline vapors from the fuel tank and pipeline system can escape into the environment and cause pollution.

Exhaust gas recirculation (EGR) system

The exhaust gas recirculation (EGR) system brings part of the exhaust gas back to mix with the intake air to help reduce Nox pollutant concentration and increase engine performance. When working for a long time, the control valve and exhaust pipes of this system become clogged with soot in the exhaust gas, causing the engine to consume fuel and reduce power. This is also one of the common phenomena that causes the check engine light to turn on. We should periodically clean the exhaust gas circulator to help the vehicle operate smoothly and reduce fuel consumption.

Thermostat valve

The thermostatic valve helps circulate coolant and ensure the temperature is between 80 – 95 degrees Celsius, helping the engine operate optimally. As the coolant flows, the thermostatic valve regulates engine temperature. But if the thermostat is stuck open, it will prevent the engine from reaching optimal power for normal operation; And when the thermostat gets stuck when closed, it will cause your car’s engine to overheat.

When the heat gauge turns into the red zone, the check engine light will light up. You need to replace the thermostat, rubber gasket, or any other damaged component.

Mass air flow sensor (MAF)

The mass air flow sensor (MAF) is responsible for measuring the intake air flow entering the engine, transferring signals to the ECM so that the ECM can calculate and adjust the appropriate amount of fuel and ignition timing. However, when operating for a long time, this sensor is also susceptible to dust and dirt, causing incorrect information to be transmitted, affecting the entire system. Therefore, if the intake air flow sensor is detected to be faulty, the Check Engine light will turn on to notify you.

Oxygen sensor

A faulty oxygen sensor is the most common cause of the check engine light coming on. Most cars have 2 or more oxygen sensors located above and below the engine.

Oxygen sensors measure emissions in the exhaust and use the data to calibrate engine power in real time. Signs of a faulty oxygen sensor are reduced engine performance and poor engine performance. If the oxygen sensor has an error, providing information to the ECU incorrectly will cause the vehicle to both consume more fuel (about 4% compared to normal) and cause the check-engine light to light up.

Catalytic converter

The catalytic converter is responsible for processing toxic components in the exhaust gas before releasing it into the environment. Problems with this part are often due to a weak ignition system, causing incomplete fuel combustion and causing goldfish errors. If the catalytic converter is malfunctioning, the car will also turn on the check car light.

This part needs to be replaced after being used for a long time, especially on very old cars. However, to protect the catalytic converter, we should also maintain it periodically like other parts of the vehicle.

What should I do when the car shows the Check Engine light?

Regardless of the situation, when your Check Engine light comes on, you should take your vehicle to the nearest reputable auto repair garage that has a diagnostic machine that can diagnose and repair your vehicle. most accurately and safely. However, how the check engine light works can help you determine the problem and its severity. You can refer to a few cases below:

Case 1: The light comes on in some conditions

Caron engine warning light

When you see the Check Engine light on, if the vehicle has minor errors, the engine can still operate normally. However, you should not be subjective because if not fixed soon, the vehicle error can become more serious. Because the engine’s operation is the coordination of many parts. If one part malfunctions, it can have a knock-on effect on many other parts.

At this time, for safety, it is best for the driver to only operate the vehicle at a speed range of less than 40 km/h. Then you should take the car to the garage to check for errors immediately.

Case 2: The light flashes continuously

In case the Check Engine light flashes continuously, this is a sign of an emergency situation, the engine may be overheating or the catalyst is overheating. If you continue to move, it can seriously damage the vehicle’s operating system and even cause the vehicle to catch fire. Therefore, it is best at this time to find a safe place to stop the car and call rescue to tow the car to the garage for inspection.

Case 3: Noticed decrease in vehicle performance

If you notice the Check Engine light coming on and there is a drop in performance, your vehicle may have switched over automatically limp mode (vehicle’s self-protection mode) to prevent further damage. In this case, you should immediately go to the nearest auto repair garage or have the car towed to prevent engine damage.

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