Why is My Check Engine Light Flashing?

The check engine light activates to draw the driver’s attention to possible vehicle engine problems. If you see this check engine light flashing, it signifies a severe issue that requires immediate attention. Whereas a steady check engine light is less urgent, indicating a need to have the car inspected.

Sadly, the check engine warning light offers little in terms of diagnosis. It’s definitely engine related, often triggered by emissions, but could be also caused by a broad range of components failing.

Yet the last thing you should do is simply ignore it. While you may not suffer immediately, an inconvenient and costly breakdown may be on the horizon.

What to Do If Check Engine Light is On

Loose Fuel Cap

You should take prompt action to diagnose and fix your engine problem. This may involve a costly trip to the local garage, or if you’re handy with a spanner, painfully diagnosing the problem yourself.

Alternatively, you could get your hands on an OBDII scanner and plug it directly into your vehicle’s onboard computer. This enables you to read specific error codes and pinpoint the source of the problem.

The check engine light is often triggered by emissions, due to problems with ignition and exhaust systems. Here are the most common causes to help you diagnose the problem yourself.

10 Common Causes of Check Engine Warning Light

1. Loose Fuel Cap

Spark Plugs

Sometimes it can be this simple! If your fuel cap is not properly fastened, your gas may slowly leak or evaporate out. This is certainly going to decrease your fuel economy. Your vehicle’s check engine light may be triggered by this directly or even as a result of related problems.

2. Spark Plugs

Spark plugs are responsible for igniting the compressed fuel and producing power within an internal combustion engine. Spark plugs are not expensive or difficult to replace, yet a faulty one will severely affect the economy and performance of your car.

If they are underperforming, they often cause check engine light flashing. When left in this state, it can damage more costly components such as the catalytic converter.

Ignition Leads3. Ignition Leads

These leads carry the electrical charge to the spark plugs, enabling a strong enough spark to ignite the fuel. If old or damaged leads cannot carry enough electrical current to spark plugs, their performance is hindered.

The negative impact is the same as with spark plugs, reduced fuel economy, and overall engine performance.

Coil Packs4.  Coil Packs

Another ignition related component is vital for providing the enough electrical charge to the spark plugs.

They can often degrade with age, especially if subjected to extreme temperatures. If damaged coil packs are left unchecked, it can soon result in further engine woes.

Oxygen Sensor5. Oxygen Sensor

The oxygen sensor ensures the correct mixture of fuel and air is being fed to your engine. It measures both the unburnt oxygen in the exhaust system and even measures the amount of fuel remaining in the tank.

A faulty oxygen sensor is going to provide incorrect readings to the vehicle’s computer. It’s likely to flag your check engine light and greatly reduce your gas mileage.

Mass Air Flow Sensor6. Mass Air Flow Sensor

Another vital engine sensor, this one controls the inlet of air to the engine. Readings by the vehicle computer to accurately calculate the fuel and air mixture.

If this sensor is defective, engine combustion can be affected significantly. It can lead to backfires, sluggish performance, and a reduced economy.

Fuel Injectors7. Fuel Injectors

Fuel injectors can be one of the most difficult components to accurately diagnose. Their failure is usually a gradual process, as they become clogged and inefficient.

Low-quality fuel and debris within the fuel tank can damage injectors, eventually causing them to fail.

Exhaust Gas Recirculation Valve8. Exhaust Gas Recirculation Valve

Named EGR for short, this value helps the vehicle control engine emissions and efficiency. If this value is faulty, it’s likely you will experience engine misfires, and reduce performance and economy.

You’ll certainly want to fix this quickly, before causing further engine damage.

Vehicle’s thermostat9. Thermostat

The vehicle’s thermostat manages the engine’s operating temperature by adjusting the flow of coolant. If this device fails your car may be liable to overheat, possibly even blowing the head gasket.

Thermostats can suffer from corrosion due to extreme temperatures, acidic environments or incorrect mixtures.

Catalytic Converter10. Catalytic Converter

Catalytic converters are notoriously expensive, they can be up to $2000 to replace! They help reduce emissions as exhaust gasses pass through precious metals such as platinum.

Not only will this problem plague you with a check engine light, but it will also affect gas mileage and even fail an emissions test.


Whether you notice your check engine light flashing or steady, make sure you deal with the problem as soon as you can.

You could make your life a whole lot easier by plugging in an OBD2 scanner. Check out our best OBD2 scanner reviews and get the best bang for your buck!