What to Do When Check Engine Light Comes On | Complete Guide

Seeing the check engine light illuminate on your dashboard can be stressful, especially if it happens while you are driving. For many drivers, it triggers immediate worry about expensive repairs or serious engine problems. The truth is, the check engine light can turn on for many reasons some minor, some more serious.

Understanding what to do when the check engine light comes on can help you stay calm, protect your vehicle, and potentially save money on repairs. In this guide, we’ll explain what the check engine light means, common causes, whether it’s safe to drive, and how to diagnose and fix the problem.

What Does the Check Engine Light Mean?

The check engine light, also known as the malfunction indicator light (MIL), is part of your vehicle’s onboard diagnostic system. When your car’s computer detects an issue with the engine, transmission or emissions system, it stores a diagnostic trouble code and turns on the engine warning light.

This light does not always mean your engine is about to fail. In many cases, it’s simply alerting you to an issue that needs attention, such as a faulty sensor or emissions-related problem. However, ignoring the warning can allow a small issue to become a costly repair over time.

The check engine light can appear in two ways:

1. Solid check engine light – usually indicates a non-emergency issue

2. Flashing check engine light – signals a serious problem that requires immediate attention

What to Do When Check Engine Light Comes On?

Knowing how to respond right away can prevent unnecessary damage and help you make smart decisions.

Stay Calm and Observe How the Car Is Running

When the car engine light comes on, pay attention to how your vehicle feels. Ask yourself:

• Is the car running normally?

• Do you notice shaking, loss of power, or unusual noises?

• Is there smoke or a burning smell?

  
  

If the vehicle feels normal, the issue may not be urgent, but it still needs to be diagnosed soon.

Check If the Light Is Flashing or Solid

A flashing check engine light indicates a serious issue, such as an engine misfire that could damage the catalytic converter. If this happens:

• Reduce speed immediately

• Avoid hard acceleration

• Pull over safely if possible

• Turn off the engine and call for roadside assistance

A solid check engine light usually means the vehicle can still be driven cautiously, but the problem should be addressed as soon as possible.

Check the Gas Cap

One of the most common and overlooked causes of a check engine light is a loose or damaged gas cap. After refueling, if the cap is not properly tightened, it can cause an emissions leak and trigger the warning light.

Remove the gas cap, inspect it for cracks, and tighten it until it clicks. In some cases, the check engine light will turn off on its own after a few driving cycles.

Can You Drive With the Check Engine Light On?

A common question drivers ask is, “Is it safe to drive with the check engine light on?” The answer depends on the situation.

When It’s Usually Safe to Drive

• The light is solid, not flashing

• The car runs normally

• No overheating, shaking, or warning sounds

In these cases, you can usually continue driving for a short time, but you should schedule a check engine light diagnosis as soon as possible.

When You Should Stop Driving

• The check engine light is flashing

• The vehicle is shaking or losing power

• You notice burning smells or smoke

• The engine temperature is rising

Continuing to drive in these conditions can lead to severe engine damage and higher repair costs.

Common Causes of a Check Engine Light

The check engine light can turn on for dozens of reasons. Below are some of the most common causes of engine light.

• A damaged gas cap can allow fuel vapors to escape, triggering the engine warning light.

• The oxygen sensor measures how much oxygen is in the exhaust. When it fails, it can reduce fuel efficiency and increase emissions.

• Worn spark plugs or failing ignition coils can cause engine misfires, rough idling, and poor acceleration.

• The mass airflow sensor helps determine how much fuel the engine needs. A faulty sensor can cause stalling or hesitation.

• A failing catalytic converter can lead to poor performance and increased emissions. Ignoring early warning signs can result in costly repairs.

Each of these issues will trigger a vehicle diagnostic trouble code, which helps identify the exact problem.

How to Diagnose the Check Engine Light

Diagnosing the check engine light is the first step toward understanding what’s wrong with your vehicle. When the light turns on, your car’s computer stores diagnostic trouble codes that point to the source of the problem. By retrieving these codes using a diagnostic scan, you can identify whether the issue is minor. Such as a loose gas cap or something that requires professional attention.

Use an OBD-II Scanner

An OBD-II scanner plugs into your vehicle’s diagnostic port and retrieves trouble codes from the car’s computer. These codes provide insight into what caused the check engine light to come on.

Many drivers choose to buy a scanner for home use, while others take advantage of a free check engine light scan offered by many auto parts stores.

Understand Diagnostic Trouble Codes

While the code itself won’t tell you exactly what part to replace, it narrows down the issue. For example:

• Sensor-related codes

• Emissions system faults

• Engine misfire codes

A professional mechanic can interpret these codes and perform further testing if needed.

How to Fix or Reset the Check Engine Light

Fixing or resetting the check engine light starts with finding out why it turned on. Sometimes the fix is easy, like tightening the gas cap or replacing a small part. You can reset the light with a scan tool, but if the problem isn’t fixed, the light will likely come back on.

Fixing the Underlying Problem

The only proper way to turn off the check engine light is to fix the issue causing it. This may involve:

• Replacing faulty sensors

• Tightening or replacing the gas cap

• Repairing ignition or emissions components

Repair costs vary depending on the problem. Some fixes are inexpensive, while others such as catalytic converter replacement can be costly.

Resetting the Check Engine Light

Many people search for how to reset the check engine light, but resetting it without fixing the problem is not recommended. While disconnecting the battery or using a scanner may temporarily turn the light off, it will usually come back on if the issue remains.

Resetting the light without addressing the cause can mask serious problems and lead to long-term engine damage.

When to See a Car Mechanic in Artarmon Sydney?

Knowing when to see a mechanic for a check engine light can save you time and money. If the light stays on after checking simple things like the gas cap, or if your car starts running rough, losing power, or making unusual noises, it’s best to get professional help. A mechanic can diagnose the problem correctly and prevent a small issue from turning into an expensive repair.

You should seek professional help if:

• The light stays on after checking the gas cap

• The car runs poorly or stalls

• The light turns on repeatedly

• You don’t understand the diagnostic codes

A qualified mechanic can perform a complete car diagnostic test, identify the root cause, and recommend the correct repairs.

Frequently Asked Questions

Why Did My Check Engine Light Come On Suddenly?

Sudden activation can be caused by sensor failures, emissions issues, or something as simple as a loose gas cap.

Will the Check Engine Light Turn Off by Itself?

Yes, especially if the issue was temporary. However, you should never assume the problem has resolved without proper diagnosis.

How Long Can You Drive With the Check Engine Light On?

If the light is solid and the car runs normally, you may drive for a short period. A flashing light requires immediate action.

Is a Check Engine Light Always Expensive to Fix?

No. Some causes are minor and inexpensive to repair, while others can be more costly if ignored.

Conclusion

Knowing what to do when the check engine light comes on can help you respond calmly and make informed decisions about your vehicle. While the warning light can indicate serious problems, it often signals manageable issues that can be resolved with early diagnosis.

By paying attention to how your car behaves, checking simple things like the gas cap, and using proper diagnostic tools, you can avoid unnecessary stress and expensive repairs. When in doubt, consult a professional artarmon mechanic and address the issue promptly — your engine, wallet, and peace of mind will thank you.