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Common Causes of a Check Engine Light

Updated: Jan 9

The check engine light is of the most infamous warning lights, an orange/yellow light appears resembling the shape of a car engine, the words "check" or "check engine" may appear along with this warning light.

Sometimes it may simply be a sensor malfunctioning and be nothing to worry about, other times it may indicate a serious issue.


Table of Contents:

check engine light on dhasboard

What Is the Most Common Cause of Check Engine Light?

The most common cause of a check engine light turning on is a faulty oxygen sensor. This sensor measures the amount of unburned oxygen in the exhaust system, and if it is not functioning properly, it can cause the check engine light to illuminate.

Other common causes of a check engine light include a faulty catalytic converter, a malfunctioning mass airflow sensor, and a problem with the ignition system.

Why Does the Check Engine Light Come On?

Several factors might cause the check engine light to come on. Simple problems like a loose fuel filler cap or serious ones like an engine malfunction might set off the alert.

Serious issues might also trigger the light. To diagnose the issue, connect it as quickly as possible to an OBD scanner device to observe if fault codes display, then see a qualified mechanic for the outcomes.

Can the Check Engine Light Come On for No Reason?

The check engine light might illuminate for a variety of causes. There is typically a cause, whether it be a small or significant one.

If nothing appears to be wrong, common emissions-related causes for a check engine light include a loose filler cap or a malfunctioning catalytic converter.

Occasionally, a loose electrical connection or sensor might turn on the check engine light.

What Causes the Check Engine Light?

There are several potential causes for the check engine light to come on. For instance, if the computer in your car detects an issue with the powertrain (the engine, transmission, and related components) that might lead to increased exhaust emissions

If the fuel cap is broken or loose, fuel vapours may leak into the environment and trigger the check engine warning. It might potentially turn on due to a misfire and the resulting greater emissions.

Depending on the year, make, and model of the car, the check engine light may come on in a different way.

Without thorough investigation by an experienced technician, it is impossible to pinpoint the precise cause of the check engine light being on.

  • When there are issues with the powertrain, the check engine light will come on (engine, gearbox, and associated components).

  • If your braking system isn't working properly, the ABS (anti-lock braking system) warning light will turn on instead of the check engine light.

But since a car's different systems are so interconnected, occasionally a problem with one subsystem (such the antilock brakes) might trigger alarms in another (such as the powertrain).

However, the CEL (check engine light) most likely signifies a problem with the powertrain and engine.

Solid vs Flashing

The importance may change depending on whether the check engine light is on all the time or flashing. A problem is indicated when the engine check light is either solid or flashing.

A serious problem that can result in further harm is indicated by a flashing engine check light. In order to prevent serious damage, you should get the car looked at if the light starts to flash.

When a situation is serious, certain cars' engine lights won't flash. The warning light could change from yellow to red or orange when a serious issue is found.

However, not all vehicles operate in this manner and usually differ. You should always get your vehicle inspected, regardless of whether the check engine light is steady or flashing.

Common Causes of a Check Engine Light

Let's explore some of the most common causes of check engine lights.

There are various causes; the ones listed here are only some of the more prevalent ones and may not include all potential causes.

1) Engine

The check engine light could come on due to a number of reasons, including engine problems. Engine performance is monitored by a collection of sensors in a control module.

The check engine light could come on if a sensor detects unusual data.

A check engine light might come on for a variety of reasons, including overheating, faulty sensors, engine failure, etc. Most of the time its a faulty sensor or a spontaneous issue which restarting the car fixes.

2) Transmission/Gearbox

Your car's gearbox sends engine power to the wheels that are in motion. Because the two parts are so connected, a transmission issue might set off a check engine light.

Most transmission issues occur on automatic gearbox vehicles.

3) Emission Control System

In today's vehicles, onboard emissions technology is widespread.

Emission control equipment examples include:

  • Catalytic converter

  • Particulate filters

  • Exhaust gas recirculation (EGR) system

  • Evaporate emissions system

Each element aims to lower exhaust emissions. The check engine light will come on if one of these systems has a problem, which is usually the case.

4) Electrical Issues

Modern car powertrains are controlled by a multitude of sensors and modules; due to their sensitivity, even a momentary fault might trigger a warning.

Oftentimes, a sensor malfunctioning is what illuminates the check engine light.

The modules are connected by way of a vast data network. Therefore, issues with sensors, modules, networks, or wiring may result in the check engine light being illuminated.

5) Air & Fuel

Your car's engine requires the appropriate ratio of fuel and air to operate properly.

The control module will generally be able to tell whether there is too much or too little of either and trigger a warning if it is out of range.

Frequently, a sensor that isn't working properly, like the O2 sensor, might produce a warning.

6) Ignition Control System

The spark plugs, coil packs, and other parts needed to ignite the mixture of air and gasoline inside the engine are included in the ignition system.

The control module monitors the ignition system, the check engine light can come on when a problem is found.

Will Low Oil Trigger It?

Some people wrongly think that a check engine light indicates that their car's oil level is low. Low oil levels are an unusual reason for the engine check light to come on, though.

Although low oil levels are a serious problem, your check engine light won't often come on as a result. However, the check engine light could come on if insufficient oil is the root of another issue.

On the other hand, your dashboard's oil warning light may turn on. This warning sign looks like an oil can with an oil droplet coming out of the spout. If this light comes on, your vehicle could require extra oil.

Can Bad Fuel Cause Check Engine Light to Come On?

It is possible for bad fuel to cause the check engine light to turn on. If the gasoline is contaminated or has gone bad, it can cause the engine to run improperly, which may trigger the check engine light.

If you suspect that bad gas may be causing the check engine light to turn on, you can try filling up your tank with fresh gasoline to see if that resolves the issue.

If the check engine light continues to come on after filling up with fresh fuel, you may want to have a mechanic diagnose the issue to determine the cause of the problem.

Is It Safe to Drive With a Check Engine Light?

Sometimes a check engine light signifies a major problem, other times it is simply a minor issue and the vehicle can still be driven. Keep close attention on your car's performance and ask yourself the following questions.

  1. Are there any unusual noises such as knocking or tapping?

  2. Is it still running smoothly?

  3. Has it lost power or does the car feel different?

  4. Are there any strange smells such as burning or exhaust fumes?

If you don't notice anything unusual while driving, it may be fine to continue driving to a safe location even if the check engine light is on.

If you want to keep on going, drive carefully, slowly, only when necessary, avoid hills, keep the RPMs low, and get it checked out and fixed as soon as you can.

Finding the Cause

A technician is equipped with the tools and equipment necessary to interpret the meaning of a check engine light.

When the check engine light on your vehicle comes on, a diagnostic trouble code (DTC) is recorded in the computer's memory.

An OBD scan tool may extract this fault code when connected to the OBD port in your vehicle, indicating the problem.

Your check engine light may be on for a cause that a fault code does not entirely explain. Instead, it acts as a foundation for more research and diagnostic tests to pinpoint the issue.

Once the issue has been identified and fixed, the engine check light should turn off automatically. If, however, it does not go away or comes back, more research may be necessary.

What to Do When Check Engine Light Comes On

Until a mechanic diagnoses your car, you won't know what the check engine light means. It might be something small or something significant that could lead to more harm.

A good idea is to use an OBD scanner to get an idea of the cause of the check engine light.

When driving, if the engine warning light comes on, pay attention for unusual noises, smells, and vibrations. It may be best to stop somewhere safe if you notice anything or if the car drives differently.

It could be safe to drive a longer distance, such as home or to a garage, if nothing appears to have changed.

Don't take any chances; as soon as your check engine light illuminates, have it examined by a professional.


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