What does Check Engine Light Flashing Means?

A solid check engine light signifies a non-urgent issue that needs addressing, whereas a flashing check engine light signals a critical problem.

Salman Chaudhary, Founder Pinkywheels.com

What does Check Engine Light Flashing Means?

Common Reasons for Your Check Engine Light

Understanding the Check Engine Light System

The purpose of the check engine light is to promptly alert drivers to potential issues within the car's management system, including the engine, electronics, exhaust, and more. This system relies on sensors strategically placed throughout the vehicle, which transmit information about any anomalies.

This innovative system replaced the traditional diagnostic approach, which relied solely on a mechanic's experience and expertise. When the check engine light activates, you or your mechanic can connect an OBD II reader to the OBD II port, read the diagnostic code, replace the problematic component, reset the light, and resolve the issue.

While this system was designed to simplify the lives of drivers and mechanics, it has both advantages and disadvantages.

The Upsides and Downsides of the Check Engine Light


  • Timely warnings and preventive maintenance.


  • The main drawback is that issues like a faulty sensor, damaged wire, or short-circuit can lead to frustrating wild goose chases, wasting time and money on unnecessary repairs.

  • In some cases, despite significant spending, the check engine light remains on, leaving drivers frustrated and mechanics scratching their heads.

  • This system, though potentially helpful, can also cause headaches for both car owners and drivers.

This article aims to help you avoid these frustrations by listing common reasons for check engine light activation, and providing guidance on identifying and resolving the issue.

1. Loose or Faulty Gas Tank Cap

Although a loose or faulty gas tank cap is often the first thing people check, it's rarely the solution. Typically, a gas tank cap loosens during refueling or develops issues with its rubber seal due to exposure to fuel over time. In either case, excessive air enters the gas tank, triggering the check engine light.

It's the simplest check to perform, and if it resolves the issue, you're in luck.

2. Faulty Oxygen Sensor (O2 Sensor or Lambda Sensor)

Faulty oxygen sensors are a common culprit. Over time, these sensors, located in the exhaust system, can become dirty or fail due to heat and material wear. Using an OBD reader is the best way to identify this problem. Oxygen sensors are often found on the exhaust manifold and pipes, and most vehicles have at least one, if not two.

Aside from sensor failure, oxygen sensors can also respond to poor-quality fuel or issues with air intake, affecting the air-fuel mixture. Replacing an oxygen sensor is usually straightforward, but it may be challenging to remove due to heat and rust.

3. Bad Catalytic Converter

A malfunctioning catalytic converter often triggers the oxygen sensor, leading to the check engine light activation. Catalytic converters are responsible for purifying exhaust fumes. Over time, they can become clogged with grit from exhaust emissions, especially in older cars or those using low-quality fuel.

The solution is to replace the catalytic converter, but this is often expensive. Avoid questionable DIY solutions like removing or cutting the converter, as they harm your car, the environment, and yourself.

4. Faulty Mass Airflow Sensor (MAF Sensor)

Another common issue is a faulty MAF sensor, which can also trigger the check engine light. The MAF sensor can become dirty and clogged, providing incorrect readings to the ECU, affecting engine management. Cleaning the sensor is a common practice, but replacement is straightforward in most cases.

5. Air Intake Problems

Air intake system faults are frequent causes of the check engine light illuminating. Loose hose clamps, damaged seals, punctured hoses, or other issues can trigger the light. Unfortunately, this can send you on a wild goose chase, resulting in unnecessary part replacements.

Checking the air intake is a DIY job, but it requires patience and a keen eye. Inspect all air intake components, including hoses, clamps, seals, and housings.

6. Car Battery Condition

Modern cars heavily rely on proper battery conditions. When the car battery begins to lose power, various problems can arise. The sensitive ECU can trigger the check engine light even when the car is otherwise fine. Battery replacement or recharging is the solution.

7. Alternator Voltage Output Problems

The alternator supplies electricity to the car's systems. If the voltage output is too high or low, it can disrupt the ECU and cause issues, including warning lights and glitches. Timely resolution is crucial to prevent further damage.

8. Worn Out Spark Plugs (Petrol Engines)

Worn-out or damaged spark plugs can lead to engine misfires and trigger the check engine light. Regular maintenance and the use of high-quality spark plugs can prevent this problem.

9. Damaged Spark Plug Cables (Petrol Engines)

Spark plug cables are more susceptible to damage than the plugs themselves. Over time, heat, vibration, high voltage, and material fatigue can cause cable wires to break or burn out. This leads to engine misfires and check engine light activation. Replacing the cables is typically a DIY job.

10. Electric or Electronic Problems

Short circuits, damaged wire insulation, and moisture near contacts can trigger the check engine light and are challenging to diagnose. The OBD diagnostics may not provide accurate fault codes in these cases. A thorough inspection of the entire electrical system is required to identify and resolve these problems.

Driving with a Check Engine Light On

Can I drive my car with the check engine light blinking?

Unlike other warning lights, the check engine light typically doesn't indicate immediate danger. However, it's advisable to stop as soon as possible when it activates and perform a quick under-the-hood inspection. If there are no major irregularities and you're not in immediate danger, you can continue driving but should schedule a thorough check-up with a mechanic promptly.

What is the difference between a flashing and Solid check engine light?

A solid check engine light signifies a non-urgent issue that needs addressing, whereas a flashing check engine light signals a critical problem requiring immediate attention to prevent further damage.

Resetting the Check Engine Light

There are several ways to reset the check engine light:

  1. Use an OBD code reader.

  2. Disconnect the battery terminal (with precautions).

  3. Repair the underlying issue, which may automatically turn off the light after a few starts.

Please note that these methods vary in effectiveness depending on your car's make and model. Always prioritize addressing the root cause of the issue.

FAQs: What Does a Flashing Check Engine Light Mean?

Q1: What does a flashing check engine light mean? A1: A flashing check engine light indicates a critical problem with your vehicle that requires immediate attention. It signifies a severe issue, typically related to the engine or emissions system, and driving with a flashing check engine light can cause further damage.

Q2: Can I drive my car with a flashing check engine light? A2: It's not recommended to drive with a flashing check engine light. Doing so may result in severe engine damage. Pull over safely, turn off the engine, and have your vehicle inspected by a mechanic as soon as possible.

Q3: Is a flashing check engine light more serious than a solid one? A3: Yes, a flashing check engine light is more serious than a solid one. A solid check engine light indicates a non-urgent issue, while a flashing one signals an immediate and severe problem.

Q4: What should I do if my check engine light starts flashing while driving? A4: When the check engine light starts flashing, pull over, turn off the engine, and do not continue driving. Contact a mechanic or a tow service to have your vehicle inspected and repaired.

Q5: Can I reset the flashing check engine light on my own? A5: Resetting a flashing check engine light should not be your first priority. You should focus on addressing the underlying issue causing the light to flash. Once the problem is resolved, the light may turn off on its own or can be reset using an OBD code reader.

Q6: Are there any exceptions to not driving with a flashing check engine light? A6: If you're in a remote area with no immediate access to help, you may cautiously drive a short distance to reach a safe location. However, this should only be done in extreme situations, as continued driving with a flashing check engine light can result in severe engine damage.

Q7: What if my flashing check engine light stops flashing? A7: If the flashing check engine light stops flashing and becomes solid, it indicates that the issue may have stabilized, but it still requires attention. Have your vehicle inspected as soon as possible to prevent any further problems.

Q8: Why does the check engine light flash? A8: The check engine light may flash due to severe issues such as engine misfires, catalytic converter damage, or other critical engine or emissions system problems. It flashes to alert you to these urgent concerns.

Check Engine Light Flashing
Check Engine Light Flashing