Intermittent Flashing Check Engine Light-Causes & Solutions

The two most frequently asked questions, “why does my check engine light flash” and “what should I do if this happens” are well explained in this comprehensive post.

Specifically, we analyze the most common causes of the intermittent flashing check engine light problem. Besides, you will get valuable advice to deal with the issue calmly and efficiently.

intermittent flashing check engine light

What Are The Common Causes Of Intermittent Flashing Check Engine Light?

Check engine light is how the vehicle’s computer, referred to as ECU(electronic control unit), indicates component’s errors.

Blinking check engine could signify either minor problems like losing the gas cap or serious irreversible damages.

Ultimately, by accurately addressing the source of the issues, you can find the most suitable solution to prevent the problem from escalating.

Now, let’s get insights into the most common question, “what does it mean when check engine light flashes?”

Loose Gas Cap

A minor problem like a faulty gas cap or forgetting to tighten it can trigger the check engine light. It addresses the failure of recirculating gasoline vapors.

The light keeps staying on until the next time you pump gas and tighten the gas cap.

As a result, checking the gas cap is the first thing you should do when your check engine light starts flashing randomly.

Gas Tank

Faulty Oxygen Sensor

Another culprit resulting in the check engine light randomly turning on and off is the faulty oxygen sensor.

The oxygen sensor measures the amount of unburned oxygen in the exhaust system and then transmits that information to the ECU.  The ECU adjusts the proper air-fuel ratio based on the oxygen level in the injection.

Consequently, if you ever notice a sudden reduction in gas mileage accompanied by check engine light flashing occasionally, the potential root cause could be the failing oxygen sensor.

Faulty Oxygen Sensor
Faulty Oxygen Sensor

Poor Electrical Connections

The damaged electrical connection of sensors could also result in check engine light flashing occasionally.

With use, the vehicle’s sensors will gradually deteriorate. Once this problem is detected, signals are sent to the onboard computer to alert drivers. Consequently, the check engine blinking is an indicator for this type of trouble.


Bad Spark Plugs

If you feel it is harder to start your vehicle or it does not accelerate correctly, your car is faced with failing spark plugs. Such kind of trouble will immediately get the check engine light flashing.

Fortunately, worn-out spark plugs do not immediately require us to pull over and park the car for emergency mechanic checks. However, we recommend you get it checked out by professionals as soon as possible.

This is due to the fact that an unchecked malfunctioning ignition system can lead to severe damage like a broken catalytic converter if the system is not fixed sooner. The replacement fee costs up to $2000.

Dirty Spark Plug

Faulty Mass Airflow Sensor

The mass airflow sensor measures the amount of air flowing into the engine. Its indication is vital for the engine computer to determine the proper fuel quantity.

The failure of the air-to-fuel ratio dramatically impacts fuel efficiency and emissions.

The buildup of dust and grimes in the air filter can eventually result in a blockage. If this blockage incidence persists, it will lead to faulty mass airflow sensors and insufficient performance.

So, regular cleaning is the best way to avoid airflow sensor error and the car engine light flashing.

Mass air flow (MAF) sensor

Low Fluids Or Non-Lubrication Of Engine

If a car engine light flashing indicates non-lubrication of the engine, your car trouble becomes very serious. The supply of sufficient lubrication is vital for the operation of moving parts under different conditions.

Based on the above knowledge, it is suggested that your car is regularly serviced instead of searching “why my engine light is blinking the first moment you see an illuminated CEL.”

 The advantage of regular maintenance is to remove dirty oils and engine sludge. Otherwise, the oil pressure sensor sends a signal to the onboard computer, causing intermittent check engine light.

Filling car power steering fluid

Fuel Ignition System Issues

Worn-out plug wire, the failing spark plugs, weak ignition, and leaking head gasket are some dominant issues of the fuel ignition system.

Moreover, rough idling, slow acceleration, backfiring, hard starts, and stalling are easily spotted if something is wrong with the fuel ignition. These noticeable symptoms show up under the catch-all “check engine” light.

As a result, the check engine light intermittent flashing serves as a warning for drivers about the malfunctioning fuel ignition.

Running a vehicle diagnostics test is advisable to devise the most appropriate solution for each particular problem.

Fuel Ignition System Issues

Is It Bad To Drive With Intermittent Flashing Check Engine Light?

After getting a thorough understanding of the question, “why is my check engine light flashing on and off”, you probably wonder if it is acceptable to drive with intermittent flashing check engine light.

The answer is it is! It is still possible for you to go a short distance at a moderate speed if you feel nothing wrong with the engine system.

It is a lot safer if you can pinpoint the root cause of the flashing engine light turning on and off randomly. The car components operate as a fully integrated body structure.

Therefore, looking up the cause of why my check engine light blinking is essential to avoid severe damage.

After a diagnostic scan, you will know that the intermittent flashing check engine light signifies engine misfiring. Then, you need to find the culprit behind the engine misfiring.

It could be caused by worn-out spark wires, faulty plugs, a faulty ignition system, or fuel system issues.

Our advice is to always keep an eye on the check engine light and conduct a vehicle diagnostics test to locate and repair the engine’s errors quickly.

How To Reset The Check Engine Light Indicator?

The first method is resetting the check engine light indicator with an onboard diagnostic (OBD 2) scanner. The second method that is equally as effective is the battery disconnection technique.

Now, let us guide you through these two methods.

Method 1: Resetting by using an OBD 2 scanner.

Step 1: Connect the scanner with an OBD connector located under the steering component.

Step 2: Turn the ignition to the ON position.

Step 3: After the successful connection between the scanner and the car computer, press the “Read” button to look up stored diagnostic trouble codes.

Step 4: Read the OBD codes

Step 5: Press “Erase/Clear” on the scanner to erase errors, then switch the ignition off.

Step 6: Switch the ignition on again and double-check if the check engine light is still flashing.

Additionally, ensure that the scanner has removed all the system’s faults before disconnecting.

Method 2: Battery disconnection

Battery disconnection is a handy method when an OBD2 scanner is not available.

Step 1: Remove the negative car battery terminal.

Step 2: Release any remaining electricity in the capacitor by either turning lights on or pressing the horn for approximately 20-30 seconds.

Step 3: Leave the car’s engine turned off for 15-20 minutes after the complete battery disconnection.

Step 4: Reconnect the battery and switch the car on.

If the intermittent flashing check engine light persists, it highlights the potential threat to the engine. Then, it is essential to read the error through an OBD 2 scanner.


  1. Why Is My Check Engine Light Blinking?

The blinking check engine light indicates a more serious fault than the intermittent flashing one. It requires an immediate mechanic to avoid severe damage.

  1. What Should I Do When Engine Light Is Intermittent?

As explained above, the check engine light on and off intermittently could highlight minor troubles.

So, firstly look at other lights on gauges. Light indicators such as low-oil pressure and overheating are used as a warning.

Stop the car and turn it off as soon as possible. If the CEL turns off, you’ve successfully fixed the problem.

Otherwise, try tightening the gas cap. It may take some tries to reset the light.

Finally, slow down the speed and park the car at the nearest automotive service center to decipher the error codes, then repair any broken parts accordingly.

  1. What Are Some Common P Codes Associated With The Check Engine Light?

Some common P codes related to the flashing of the check engine light are:

P0401 – Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

P0299 – Turbocharger/Supercharger A Underboost Condition

P0300 – Random Misfire Detected Code

P0420 – Catalyst system efficiency below threshold 

P0440 – Evaporative Emission Control System Malfunction


We hope the post relieves your worries if you ever encounter the intermittent flashing check engine light problem.Most importantly, regular maintenance is the key to preventing engine issues.

It will help reduce the unfortunate occasion where you have to wonder, “why would my check engine light be flashing” thus resulting in a pleasant user experience.

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