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Check Engine Light Flashing: Causes and Fixes

Content Overview

A flashing check engine light usually indicates a severe issue that requires immediate car repair. Issues that cause the engine lights to flash include an engine misfire, a loose fuel cap, and bad oxygen sensors.

Unfortunately, the check engine light flashing is something a lot of drivers tend to ignore. A study by the automobile research team of Reviews.com found that only 36% of drivers get their check engine light inspected within the week when it first flashed. The study's other troubling findings include:

  • 25% of people said they never get the check engine light code inspected.
  • 29.6% stated they wait between a month and a year before they have the check engine light inspected.
  • 9.2% said they wait until an obvious problem shows up.

One anonymous person in the study also mentioned that they don't want to know what's wrong because it's probably something they can afford. While this sentiment is understandable, it is still crucial to have your blinking check engine light checked for your safety and maintain the car's integrity.

This article will talk about what a check engine light is for, why it's flashing, and what you can do to fix it.

What is a Check Engine Light?

The check engine light or the malfunction indicator lamp is a signal from the engine's computer that indicates something is wrong. The check engine light is found on the dash and often shows up as an engine symbol. The symbol can be replaced by either a "check engine" or "service engine" sign on some makes of cars.

The Different Types of Check Engine Light Illumination

car dashboard

Drivers can get a clue on the severity of the problem by checking how the check engine light is flashing. There are three types of illumination:

  • Continuous: If the light is on but not flashing, it means there's no major issue with the car. The fix could be straightforward and less threatening. A continuous light may start by flashing but eventually becomes stable.
  • Intermittent: The check engine light blinks for a while and then turns off by itself. This indicates a possible soft failure. It can be an issue with the car's wiring being cut or constantly being disconnected.
  • Continuous Flashing: If the check engine light is constantly flashing, this indicates an emergency. A serious problem may have been detected, and you need to take the car to an auto care professional.

The engine light color is also an important indicator. In some modern or high-end cars, a red check engine light indicates imminent danger that requires immediate attention. A yellow light warns drivers that there is an issue that needs to be resolved soon.

What Causes a Flashing Engine Light?

If the car's onboard diagnostics system (OBD II) detects a malfunction in the vehicle's ignition, emissions, fuel, or exhaust systems, the check engine light flashes on. An engine light flashing may have a number of causes, but the car needs to be inspected to determine these reasons.

The OBD II usually records the cause of the blinking engine light through codes, which are read by professional mechanics' decoders. The following are the common reasons the check engine light flashes.

A misfire happens when one or more cylinders fail and no longer supply enough power to the engine.

1. Engine Misfire

under a car's hood

One of the most common causes of a flashing check engine light is a misfire. Every cylinder in your car has to provide the right amount of power to the engine to run properly. A misfire happens when one or more cylinders fail and can no longer supply enough power to the engine.

There are three main reasons your vehicle misfires:

  • Ignition Issues: This is the most common cause of a misfire. Ignition system problems include improper ignition timing, or the plugs aren't providing a spark to the cylinders. It happens due to the normal wear and tear of ignition parts.
  • Fuel Mixture Problems: Every cylinder needs a proper mix of fuel and air. If the mixture has too much air, it causes slow acceleration and backfiring. If there's too much fuel, it can cause overheating and sluggish acceleration. All this can be caused by faulty fuel system components like fuel injectors and pumps.
  • Low Compression: When one or more cylinders leak fuel or air, a compression loss happens. The cylinders don't generate the right amount of pressure. Low compression results in low power, slow acceleration, and heavy shaking in the cabin. Common causes include gasket leaks, holes in the piston, or a bad timing belt.

How To Fix an Engine Misfire

car engine

Conducting engine diagnostics is an important first step. A good way to do this is through the use of a diagnostic scanner. When the check engine lights flash, the OBD II records the issue using codes that can be read with a diagnostic scanner.

For a misfire, the scanner should show the code P0300. It confirms that the issue is, indeed, a misfire. Some professional scanners can also indicate the specific cylinders that need fixing. Depending on the affected cylinder, one of these can show up:

Cylinder 1 misfire – P0301

Cylinder 2 misfire – P0302

Cylinder 3 misfire – P0303

Cylinder 4 misfire – P0304

Cylinder 5 misfire – P0305

Cylinder 6 misfire – P0306

Once a professional car repair specialist determines the cause of the problem, they can physically inspect the engine and fix it.

For ignition issues, replacing spark plugs and ignition coils is usually the best solution. On average, it just takes an hour of labor. The cost depends on the service:

  • Replacing Spark Plugs ranges from $20 to $100
  • Replacing Ignition Coils are around $300, depending on the car make and model

Fuel mixture and low compression problems are more complicated and costly to repair. They often involve a significant amount of labor. These solutions include:

  • Replacing intake manifold gasket: Around $420
  • Replacing fuel injectors: Averaging $480
  • Replacing catalytic converter: Ranging from $900 to $3000, depending on the vehicle

2. Loose Fuel Cap

When you notice the check engine light blinking, stop the car and check the fuel cap. It might be loose.Check if there are any cracks, chips, or tears in the fuel cap. Check the seal between the fuel cap and the filler tube to see if any cracks are present.

If you are satisfied that the fuel cap has no damage, place it back into the filler tube and tighten the cap until you hear a click. The check engine light should return to normal after a few minutes.

If you noticed any cracks or tears on the fuel cap or the filler tube, replacing them should solve the issue. Ignoring the problem may cause fuel vapor leaks that could cause major problems over time.

Average repair cost: Around $5

3. Faulty Airflow Sensor

An airflow sensor calculates the exact amount of fuel to mix with the oxygen within the engine. When the sensors fail, the fuel economy is reduced by up to 25% and triggers the check engine light to flash.

With a faulty air flow sensor, you will still be able to drive your car but with subpar performance. Fortunately, replacing the sensor can be done easily and quickly by a professional mechanic. You can even include this during your next oil change.

Average repair cost: $250 to $450

4. Failed Oxygen (O2) Sensors

Your vehicle's O2 sensor monitors how much oxygen and unburned fuel is exhausted. This sensor is a critical part of the exhaust system and is located inside the exhaust pipe. Like the airflow sensor, this shouldn't stop you from driving the car.

However, a faulty O2 sensor will reduce fuel economy and eventually damage your car's catalytic converters, which are expensive to replace. It is best to have a bad O2 sensor to be replaced as soon as possible.

Average repair cost: $150

5. Evaporative Emissions Control (EVAP)

The EVAP system prevents fuel vapors in the fuel tank and fuel system from escaping into the atmosphere. It is composed of various components that can trigger the check engine light should they malfunction. Some of these components and their repair costs are:

  • Canister vent valve: $208
  • Purge solenoid: $196
  • Vent control valve: $249
  • Purge control valve: $176
  • Solenoid: $221

How To Reset Check Engine Light

car dashboard

Once repairs have been carried out in an auto service center, the mechanic would have reset the check engine light before turning the vehicle over to you. However, if you did the quick fixes yourself, there are three ways to reset the engine light:

  1. Use your OBD II scanner and connect it to your vehicle. Choose the "Erase/Clear" option, and the light should switch off. If it doesn't, turn off the engine and turn it on again after 3 to 5 minutes. Try switching off the check engine light again.
  2. If you have no scanner, disconnect the battery. Remove both positive and negative terminals and leave them for at least 15 minutes. Re-attach them again and start the engine. The light should be off.
  3. If you are sure that you made the necessary fixes, leave the light on. The check engine light will automatically reset after a 3-day engine cycle. If the light still shows up, run another diagnostic test and check for further issues.

Why You Shouldn't Drive with A Flashing Check Engine Light

A flashing check engine light is a serious symptom that requires immediate inspection and repair. If you are driving and suddenly notice your check engine light blinking, there's a chance your vehicle might overheat.

An engine misfire can impact your ability to accelerate, making you a potential hazard to other drivers.

It doesn't matter if your vehicle is well-maintained or you own a top-of-the-line car. You must pull over to the side of the road, turn off the engine, and investigate the problem. If it's something you can't fix, call for auto repair help and wait until it arrives.

Get your vehicle towed to a qualified mechanic. While towing bills are expensive, engine repairs or replacements are more expensive—not to mention the potential accidents that could happen.

An engine misfire, for example, can affect your ability to accelerate, making you a potential hazard to other drivers. When an engine misfires, fuel can also pass through the exhaust system and to the catalytic converter. The converter will turn excess hydrocarbons, carbon monoxide, and nitrogen oxides into harmless compounds.

However, the catalytic converter needs to work at extremely high temperatures. The fuel passing through the exhaust system can ignite and destroy the converter, which is a very expensive problem to have.

One in seven motorists drives with a potentially serious issue in their car. Fifteen percent of the commonly identified problems is the check engine light turned on. You might be tempted to ignore the engine light in your desire to get to your destination quickly, but addressing it not only keeps your vehicle safe but also saves you from future unnecessary expenses.

At the first sign of engine light problems, it's best to turn to a professional for assistance. Auto Works of Brandon has over 20 years of experience in providing auto diagnosis, complete car maintenance, and repair solutions.
Our company also specializes in various European and import vehicles like BMW and Mercedes Benz. Get in touch with us today and schedule an appointment for auto repair or maintenance.

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