What Does it Mean When the Check Engine Light Comes On?

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The check engine light is one of your car’s dashboard symbols – it’s an orange engine-shaped icon set amongst your dashboard lights that illuminate to alert you on your car’s health.

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What is a Check Engine Light?

The check engine light either flashes or is steady depending on the severity of the car issue.

For most car owners, car light symbols such as a check engine light suddenly appearing can be frustrating and confusing to understand.

That’s why we’ve prepared these tips to help you figure out the most probable causes – saving you money and unnecessary worry.

The best way for non-mechanics to clear your engine light is to use a diagnostics tool.

Ready to demystify the check engine light? Let’s go!

How the Check Engine Light Comes On

If your car was built from 1996 onwards, it is fitted with an onboard diagnostic system (OBD2). The OBD2 system has a self-diagnostic and reporting capability.

Using a scan tool inserted in the OBD port, it sends OBD codes that enable you or your mechanic to identify malfunctions in the vehicle. The check engine light is simply part of the OBD2 system.

But there’s one problem, the OBD codes can be hard to understand if you are using a typical scanning tool.

Luckily for most of us, it’s now possible to read your car’s OBD2 codes in plain English and know your car’s exact problem using an economical and user-friendly scan tool.

Here’s are some more functions of the OBD2 system:

  • Control and monitor vehicle performance
  • Regulate engine speed, fuel mixture, and ignition timing
  • Tell the automatic transmission when to shift

Why the Light Turns Yellow

The Electronic Control System (call it your car’s brain) works round the clock adjusting problems in your car. However, when it finds a problem it can’t adjust, it turns on a yellow warning indicator.

It then stores the trouble code known as Diagnostic Trouble Code (DTC) in its memory.

The DTC codes are useful in identifying the most likely source of your car’s problem. You would need to use a diagnostic computer or a scan tool to access these codes and use them for your own testing and repairs.

Related: Car Warning Lights Resource Centre

Types of Engine Light

So we agree that when the engine light illuminates it means there’s a problem with your car’s performance, right? But what kind of problem really? Let’s dig deeper.

Steady light: It means there’s a problem but it’s not an emergency. Nonetheless, you should schedule an appointment with a qualified service technician as soon as possible. Don’t wait for the problem to escalate and cause further damage.

Blinking light: It indicates a severe engine misfire. The emissions output and safety of the vehicle are affected. Such a misfire allows unburned fuel to be dumped into the exhaust system.

This dumped unburned fuel can quickly raise the temperature of the catalytic converter to a point where damage is likely. And that can only mean an expensive car repair.

What to do? If the engine light is constantly flashing, your can engine can be seriously damaged. Switch off the engine at the nearest safe place and have your vehicle checked.

Be warned that today’s automotive computers try to compensate when there’s a problem.

And as a result, you may not notice the declining performance of your car despite your fuel mileage suffering and your car emitting unacceptable levels of pollutants such as hydrocarbons.

Also, the check engine light should not be confused with the maintenance reminder or the service interval light.

These lights will always illuminate when a service is due because they are triggered by mileage, or amount of fuel consumed.

Gofar app engine light diagnostic

Handle Check Engine Light ON Like a Pro

1. Look for a Serious Problem

Check your dashboard symbols and dashboard lights for indications of low oil pressure or overheating. These problems require immediate attention.

So, if you notice them pull over when safe and shut off the engine.

2. Faulty Gas Cap

A loose, damaged, or missing gas cap can trigger the engine light to come on. A faulty gas cap will cause a loss of fuel through evaporation and more trips to the gas pump which is expensive.

This is because a gas cap is responsible for:

  • Sealing the fuel system
  • Helping maintain pressure within the fuel tank
  • Preventing release of gasoline/petrol fumes (hydrocarbons) into the atmosphere

Just by tightening a loose gas cap or replacing it, you will often fix the problem and reset the engine light.

3. Bad Catalytic Converter

A catalytic converter converts a vehicle’s harmful carbon monoxide into carbon dioxide. Mainly to help protect our environment.

A faulty catalytic converter will cause your vehicle to:

  • Fail the emissions test
  • Suffer reduced car performance and fuel economy
  • Run at a higher temperature

If you identify the catalytic converter as the issue, replace it and the check engine light will reset.

4. Bad Oxygen Sensor

Your car’s oxygen sensor measures the amount of unburned oxygen in the exhaust system. A faulty one means:

  • Your car engine will burn more fuel than needed
  • Lost fuel economy as you’ll cover fewer kilometres per litre
  • Faulty sensors can damage your car’s spark plugs and catalytic converter

Replacing a faulty oxygen sensor will reset the engine light on your dashboard lights.

5. Faulty Spark Plugs or Spark Plug Wires

Spark plugs ignite the air/fuel mixture in your car’s combustion chamber. On the other hand, spark plug wires deliver the spark from the ignition coil to the spark plugs.

Worn out spark plugs and spark plug wires can result in:

  • Poor car performance
  • Reduced engine power
  • Poor fuel economy
  • Clogged catalytic converter
  • Damage to ignition coils and oxygen sensor.

If they are faulty, you can have them replaced and your engine light will go off.

6. Mass Airflow Sensor

The mass airflow sensor measures the amount of air entering your engine. It’s then able to determine the amount of fuel needed to run your car engine efficiently.

A faulty mass airflow sensor can cause:

  • Damage to your catalytic converter, oxygen sensors, or spark plugs.
  • Reduced car performance
  • Reduced fuel economy

7. Engine Overload

A load on the engine such as towing a trailer can affect your vehicle’s performance and cause it to lose power. In such a scenario, reduce your speed and the load on the engine.

Then, have your vehicle checked to counter further damage.

Problem Fixed?

As we’ve seen, all these car issues can be fixed either by you or a mechanic. It’s a no-brainer that you can tighten a loose gas cap.

However, some issues will need you to take your car to a professional who with a scan tool will read and interpret the diagnostic trouble codes.

Want to try it yourself? Ok, but there’s one (potential) problem: the code testing procedure must be done in absolute sequence. Skipping some tests or performing steps out of sequence can make the entire process worthless.

Even close doesn’t count. Frustrating, right?

Maybe you’re wondering if there’s a better way to understand your car’s issues right away. Something that could monitor your car 24/7 while you’re on the road and alert you when there’s a problem – in plain English.

No more confusing check engine codes and other tech lingo.

A brilliant and affordable little device called GOFAR helps you monitor your car’s health AND gives you timely alerts (in plain simple English) when your car has a fault.

That way, you’ll deal with each problem firsthand before it becomes expensive. Understanding your car just got easier with GOFARCheck it out now.

Danny Adams sitting in a chair with a laptop

Danny Adams

Co-founder of GOFAR and with a Computer Science background from Harvard University, and a Bachelor of Aerospace, Aeronautical & Astronautical Engineering (Honours), UNSW. I want to transform data from cars into useful services so -> drivers save time & money -> emissions fall -> Australian roads are safer. So we built an ATO-compliant logbook app called GOFAR. I write to help you understand how to use GOFAR to maximise business travel. Reach out via support@gofar.co.

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This content is provided for general information purposes only and does not constitute professional advice from GOFAR. We recommend consulting with an independent legal, taxation, or financial expert to ensure the information is applicable to your specific situation. Please note that relevant regulations and laws may evolve over time.