Why is my check engine light flashing then stops & how to fix it?

Although the car can't talk to you, it does communicate with you through sounds, ICONS, and messages. On the dashboard of your car, there is a common yellow engine light icon. The check engine light flashing when the vehicle's onboard computer detects some problems.

If you see the check engine light flashing, please check it as soon as possible. A check engine light that flashes and then stops usually indicates that there may be a serious issue with your car, typically caused by engine misfires, ignition system failures, or problems with the emissions control system. While a check engine light that flashes then goes off is not as serious as a continuously flashing check engine light, it does not mean you can ignore it. If you see the check engine light flashing and then stops, please have it checked as soon as possible, but there’s no need to panic; there are various ways to fix these issues. This article will explain why your check engine light may flash and then stop, as well as how to address this problem.

Flashing check engine light

What does it mean when the Check engine light flashes and then stops? 

When a vehicle's onboard computer detects a problem, the check engine light will flash. There are generally two scenarios for a flashing check engine light: it can either flash then goes solid or it can flash and then stop.

In either case, a flashing check engine light typically indicates that you are facing a serious issue, such as engine misfires, catalytic converter problems, significant fuel system failures, or emissions control system issues. These are all very dangerous signals.

If the check engine light flashes and then stops, it does not mean you can ignore it. This usually indicates that your vehicle has an intermittent issue that could lead to serious problems or critical engine issues that need immediate attention. For example, your car's catalytic converter may be on the verge of failure. Sometimes, a flashing and then goes away check engine light may simply be caused by minor engine misfires, a loose gas cap, or similar reasons. Regardless, it is not advisable to continue driving the vehicle when the check engine light is flashing and then stops, as this could cause further damage to the engine or other components. The best course of action is to safely pull over and turn off the engine, then contact a qualified mechanic or have the vehicle towed to a repair shop for diagnosis and resolution of potential issues.

Check engine light flashing then goes solid vs  flashing then stops

Why is my check engine light flashing then stops? 

A blinking engine light typically indicates a significant problem or malfunction in your vehicle's engine or related systems. Here are 8 common reasons why your check engine light come on and off：

Engine misfire:  Engine misfire occurs when the fuel-air mixture in one or more cylinders fails to ignite properly. This misfire can be caused by various factors, such as ignition coil failure, spark plug issues, injector problems, or oxygen sensor malfunctions. Engine misfires are one of the reasons for the check engine light to turn on and off. Sometimes, this engine misfire is accompanied by symptoms such as the car shaking.

Solution: Have a qualified mechanic inspect the vehicle to identify and resolve the underlying cause. 

Catalytic converter problem: Catalytic converters help reduce harmful gases emitted by vehicles. When a catalytic converter fails, it not only affects the vehicle's emissions control system but also poses health risks due to the exhaust gases released. This failure may be caused by damage or blockage of the converter, which typically triggers the check engine light. Sometimes, this catalytic converter issue is also accompanied by symptoms such as poor acceleration.

Solution: Purchase or replace the catalytic converter. The replacement cost varies depending on the vehicle model, brand, and other factors, typically ranging from $1,000 to $3,000. If considering a used catalytic converter, the price may be more economical. 

Oxygen Sensor Failure: The oxygen sensor monitors the oxygen content in the exhaust system and provides feedback for the appropriate fuel-air mixture. If there is a problem with the oxygen sensor, it can affect fuel efficiency and emissions. Oxygen sensor failures are typically caused by carbon buildup, high temperatures, and other factors, and they can lead to a flashing check engine light.

Solution: Contact a professional to inspect the oxygen sensor and determine whether it needs to be replaced based on the situation. 

Loose Gas Cap: A missing or damaged gas cap can allow gasoline to come into contact with outside air, creating potential safety hazards. If the gas cap is not tightened properly, the emissions control system may detect abnormal pressure in the tank, causing the check engine light to illuminate.

Solution: After pulling over and turning off the engine, tighten the gas cap, and then drive for a while. In most cases, the check engine light will turn off automatically. If the check engine light remains on, consider replacing the gas cap (replacement costs are typically around $20) or visit a repair shop to check and clear the fault codes.

Thermostat Valve Failure: The thermostat valve ensures that the engine operates at optimal stability. If the thermostat valve fails, it can cause the engine temperature to overheat during driving, leading to the check engine light illuminating and flashing.

Solution: Have the thermostat valve checked promptly and replace it if necessary. It is advisable to contact a professional mechanic to help resolve the issue.

Mass Airflow Sensor Failure: The MAF sensor is responsible for measuring the amount of air entering the engine. If the MAF sensor fails, it can cause the engine control unit (ECU) to incorrectly calculate the fuel injection amount, resulting in either a rich or lean fuel mixture. Once it fails, it may trigger the check engine light.

Solution: Clean or replace the MAF sensor. To avoid damaging sensitive components, it is advisable to contact a professional for cleaning or to replace the MAF sensor with a new one.

Fuel System Issues: Problems in the fuel system, such as fuel pump failure, injector malfunction, or a clogged fuel filter, can lead to an imbalance in the air-fuel mixture, which may cause the check engine light to flash.

Solution: Clean or replace fuel system components, and check the operation of the fuel pump and injectors to ensure they are supplying fuel properly. Address any fuel system issues identified during the inspection.

Ignition System Issues: Faulty spark plugs or ignition system components can cause the engine to run unstable, triggering a blinking check engine light. It is important not to ignore a flashing check engine light, as it indicates that there may be serious problems. Continuing to drive the vehicle while the engine light is flashing can lead to further damage or even breakdown.

Solution: Inspect and replace any worn or damaged spark plugs, ignition coils, or ignition wires. Additionally, check the connections in the ignition wiring to ensure there are no loose or damaged wires. It is advisable to have a qualified mechanic perform the inspection to diagnose and resolve the underlying issues.

In summary, the reasons for a flashing check engine light that then stops can typically be categorized into five main types: sensor failures, fuel system issues, ignition system problems, emissions system issues, and mechanical engine failures. If diagnostics reveal any faulty sensors, such as the oxygen sensor or mass airflow sensor, they should be replaced as needed. For fuel system or ignition system issues, relevant components should be cleaned or replaced based on the situation. If there are emissions system problems, it is necessary to visit a professional repair shop for inspection. Addressing the issue of a flashing check engine light that then stops requires specialized knowledge and tools; therefore, it is advisable to go directly to a repair shop to seek assistance from technicians for diagnosis and repair to avoid further damage.

How to fix a flashing check engine light then stops?

When faced with a flashing check engine light, you may feel confused and anxious. Therefore, in addition to understanding why the warning light is on, you also need to have some knowledge to address the issue, or, to avoid encountering this situation again in the future. 

Retrieve diagnostic trouble codes (DTCs): Retrieval Diagnostic Fault Code (dtc): A diagnostic fault code is a digital universal identifier of the fault state recognized by the on-board system. If we send the car for service when there is a fault in its operation, the repairman will use a professional diagnostic instrument (OBD-II scanner) to read the fault code of the current vehicle and retrieve the dtc from the vehicle's on-board diagnostic system. These codes will provide specific information about the detected problem, helping to narrow down potential causes. Common diagnostic fault codes include P0300, which indicates an irregular engine or a fire in multiple cylinders, and P0171, which indicates a poor fuel system.

Interpret the DTCs: Understand the meaning of the retrieved DTCs to determine the nature of the problem. This will guide you in identifying the specific component or system that requires attention.

Inspect components and systems: Perform a visual inspection of the engine, electrical connections, hoses, and other related components. Look for signs of damage, loose connections, or leaks. Address any visible issues.

Clear DTCs and test drive: After addressing the identified issues, clear the DTCs using the OBD-II scanner. Take the vehicle for a test drive to ensure that the issue has been resolved and that the check engine light no longer blinks.

Regular maintenance: To prevent future issues, adhere to regular maintenance schedules. This includes regular oil changes, air filter replacements, spark plug replacements, and other recommended maintenance tasks specific to your vehicle.

It's important to note that the specific steps and components to address when fixing a blinking check engine light may vary depending on the cause of the problem and the vehicle's make and model. If you're unsure or unable to address the issue yourself, it's recommended to seek the assistance of a qualified mechanic.

Here is a useful video to help you understand a flashing check enghine light: