Check Engine Light Flashing vs Solid: What Are The Differences?

I used to think the check engine light meant the same whether flashing or solid. But over time, with my experience dealing with cars and engine issues, I’ve realized that how the check engine light is displayed determines how severe the issue is.

The significant difference is that a solid check engine light is usually a minor issue that does not require you to rush to a mechanic. In contrast, a flashing check engine light indicates a major issue that requires urgent attention.

In the following sections of this post, I’ll explain the differences in detail and show you what to look out for when your check engine light is solid or flashing.

check engine light on car dashboard

Flashing Check Engine Light vs Solid Check Engine Light

FeatureFlashing Check Engine LightSolid Check Engine Light
SeverityIndicates a more severe and immediate issue.Indicates a less urgent issue, requiring attention but not immediate action.
MisfireOften indicates an engine misfire, such as a faulty spark plug, ignition coil, or fuel injector.May not necessarily be related to engine misfire, but could indicate various issues.
Catalytic Converter DamageSuggests a risk of catalytic converter damage due to unburned fuel entering the exhaust system.Does not specifically suggest an immediate risk to the catalytic converter.
Driving RecommendationsYou’ll need to avoid extensive driving. Immediate attention is needed to prevent further damage.Generally safe to continue driving, but the issue should be addressed promptly.
Diagnostic RecommendationsRequires immediate diagnostics to identify and address the critical problem.Requires diagnostics to identify and repair the issue, but urgency is lower.
Emissions IssuesMay be associated with severe emissions problems.Often related to emissions control system issues, such as faulty oxygen sensors or loose gas caps.
Driving PermittedAvoid extensive driving. Immediate attention is recommended.Generally safe to continue driving, but prompt attention is still necessary.
Common CausesEngine misfire, severe fuel system issues, critical sensor failuresEmissions control system problems, sensor malfunctions, minor fuel system issues.
Potential ConsequencesContinued driving may lead to further engine or emissions system damage.This may result in decreased fuel efficiency, increased emissions, or potential for more extensive issues over time.
Repair UrgencyUrgent. Immediate attention and repair are crucial.Important. Should be addressed promptly, but may not require immediate action.

Causes of a Flashing Check Engine Light

1. Misfiring Engine

A misfiring engine is when one or more of the engine’s cylinders fail to fire in the correct order. When the check engine light flashes, you may notice misfire at idle and low RPM.

This disruption can lead to several problems, from the engine juddering and showing a lack of power to an increase in fuel consumption and a strong gasoline smell.

Continuous misfires can overheat the catalytic converter, a vital component responsible for reducing harmful exhaust emissions.

Over time, this can lead to significant damage and result in expensive repairs.

2. Damaged or Clogged Fuel Injector

Fuel injectors play a pivotal role in your engine’s health. They meticulously spray fuel into the combustion chamber, ensuring a balanced burn.

However, if they become damaged or clogged, they might deliver an incorrect amount of fuel.

This imbalance can cause inefficient combustion, resulting in symptoms like engine misfires, poor acceleration, a drop in fuel efficiency, and a detectable gasoline smell.

Furthermore, persistently driving with a faulty injector can decrease the engine’s lifespan.

3. Damaged or Clogged EGR Valve

The Exhaust Gas Recirculation (EGR) valve has an environmentally friendly purpose.

By recirculating a fraction of the exhaust gas back into the combustion chamber, it effectively reduces nitrogen oxide emissions.

However, should this valve malfunction, either through damage or clogging, it can influence the engine’s overall performance.

You might notice a decrease in power, a pinging noise during acceleration, and even a reduced fuel economy.

4. No Air Supply

If anything disrupts the air supply in the engine, this delicate balance is thrown off-kilter.

An engine deprived of adequate air can experience difficulty during startup, frequent stalls, and uneven idling.

More than just an inconvenience, this issue can lead to long-term engine strain.

5. Faulty Ignition Coils or Spark Coils

The spark plugs’ responsibility is important – they ignite the air-fuel mixture, enabling combustion.

Ignition coils ensure these plugs receive the high voltage they need. However, if these components falter, the engine can misfire.

This malfunction might cause unburned fuel to seep into the exhaust, posing a risk to the catalytic converter.

Over time, this can compromise engine performance and increase repair costs.

Causes of a Solid Check Engine Light

1. Loose or Damaged Gas Cap

A simple yet crucial component. The gas cap seals the fuel system and helps maintain the fuel vapor pressure necessary for the engine.

If it’s loose or damaged, fuel vapors can escape, leading to reduced fuel efficiency and increased emissions.

Symptoms of a loose gas cap include the smell of gasoline around the car and decreased fuel economy.

2. Issues with the Mass Air Flow Sensor

The MAF sensor measures the quantity of air entering the engine, which is essential for the engine’s computer to balance and deliver the correct fuel-air mixture.

A malfunctioning MAF can lead to poor performance, reduced fuel economy, and increased emissions.

For this, you might experience difficulty starting the car, the engine stalling soon after starting, or uneven idling.


Seeing the check engine light show up on your dashboard can give an uneasy feeling. But before you start panicking, it’s important that you understand the differences between a flashing light and a solid one.

A flashing check engine light signifies a serious issue that requires immediate attention while a solid light signifies a minor issue that may not require immediate attention.