Engine Troubleshoot

Why Is The Check Engine Light Flashing? (Causes, Symptoms and Solutions)

check engine light flashing
Written by The Motor Guy

What is the meaning of a Flashing Check Engine Light?

blinking check engine light

Modern engines are complicated and it can be difficult to figure out what is wrong when you see the check engine light

A flashing check engine light is usually a sign that something isn't right with the engine in your car. 

Unfortunately if you don't have access to an OBD diagnostic tool, it's sometimes not that easy to figure out what exactly the flashing light is trying to tell you.

It's usually not a good idea to ignore a flashing check engine light.

The blinking light is on to warn you about something wrong, so what happens next will depend on the steps you take to figure out what's wrong. 

So let's explain what the check engine light is for, what causes it to light up and what you should do when you see it flashing.

What is the Check Engine Light And What Does it Do?

The Power Control Module (PCM) also know as Electronic Control Unit (ECU) is constantly receiving information from its sensors and using this information to control the various engine systems to keep the engine running smoothly.

The instrument panel on most cars and trucks will give you an idea of what the ECU is up to.

When you start up the engine, you'll usually see a few different lights flash on and then off in the instrument cluster. This is the ECU doing a check of the various engine and car systems such as fuel delivery, engine temperature, airbags, the ABS system among others. 

If everything is ok, all of the lights will go out.

One light that you won't always see is the check engine light. On some cars this will flash on for a second when the engine starts and then will go out again. On many newer cars, you'll never see this light unless there is a problem.

So the first time most people will see the check engine light flashing at them is when there is something wrong. 

Essentially, the check engine light, is there to tell you that the ECU has detected something wrong with the engine.

Depending on the make and model of your car, the light may flash continuously, illuminate constantly and be orange or red in colour. 

It's important to check right away what the engine light is trying to tell you, and the best place to start is by checking the user handbook that came with your car.

What Does A Blinking Check Engine Light Mean?

Usually, the ECU will only light up the check engine light when there is something wrong. 

But if there is a severe engine problem detected, it may cause the engine light to flash on and off to get your attention. It's very important that you take action right away.

In fact, some vehicle manufacturers call the check engine light the SES (service engine soon) light. So a blinking SES light is the ECU telling you to service the engine NOW.

Why Is the Check Engine Light Flashing?

The check engine light flashes because the ECU has detected a misfire condition on your engine and a problem with one or more engine components.

The ECU is constantly checking your engine performance by receiving real time information from its sensors. As soon as a problem is discovered the ECU reacts, by comparing sensor information that it is expecting with actual live information.

If it receives a value that is out of range, then it will trigger the Check Engine Light on the dashboard. Depending on the problem, the check engine light can turn a constant red, yellow or will flash.

What Are The Possible Causes for The Check Engine Light Flashing?

There are usually two engine systems that could be responsible for an engine misfire and a subsequent blinking check engine light.

The ignition system and the fuel delivery system.

A faulty ignition system will not be able to ignite the fuel properly and thus cause a misfire. On the other hand, a poor fuel delivery will cause a lean mixture condition that also will trigger engine misfires.

The following is a guideline of common causes for engine misfires.

1. Ignition System

2. Fuel Delivery System

Diagnostic OBD reader

In most cases, using a professional automotive scanner is the best way to diagnose and determine what component is at fault.

What Engine Misfire Symptoms Should you Watch Out for?

Along with a blinking check engine light, you may experience one or several of the following symptoms:

  1. Rough idle
  2. Difficulty in starting your engine
  3. Poor fuel performance
  4. Lack of power
  5. Distinctive misfire sound on your engine
  6. Gas smell on your tailpipe
  7. Rotten eggs smell coming from your tailpipe
  8. Black smoke coming from your tailpipe

Is it Safe to Drive with the Check Engine Light Flashing?

You should not drive your car if you suspect it is misfiring, as doing so can cause severe damage.

Depending on the components involved the risk of damaging your engine can vary from medium to high. One thing is for sure, the misfire WILL damage your engine. 

In order to give you some perspective, the following are only a few of the possible consequences of driving with the check engine light flashing:

  1. Catalytic converter collapse. As a direct consequence of engine misfire, you may face a melting catalytic converter. Not only the catalytic converter is expensive, but also could cause other costly issues like engine overheating. 
  2. Engine overheating. With or without the CAT issue you could face an overheating problem. This, in turn, can potentially destroy your engine, starting with your head gasket.
  3. Cylinder head gasket failure. A burnt head gasket is something you should avoid at all costs. It can mix your engine oil with antifreeze and ruin your main bearing. That would mean a major engine repair, way more expensive than a catalytic converter.
  4. Piston head failure. Continued misfires can break your piston head easily. Similar than the prior point, a broken piston head will force you to perform a major and costly engine repair.
  5. Burnt exhaust valve(s). Another mechanical issue triggered by engine misfires is the possibility to burn an exhaust valve. Even when this reparation doesn’t necessarily involve a complete engine repair, it does cost money.

What should you do when the Check Engine Starts Flashing?

what to do when you see  check engine light

Hopefully, after reading this article, you should be conscious of the risks associated with engine misfires. If so, you will agree that the best strategy you can follow when your check engine light starts blinking is finding a suitable place to pull over. 

Once you are parked perform a quick inspection of your engine status:

  1. If possible, take note of the engine coolant temperature value in the instrument panel. Kill the engine immediately if you suspect the temperature is above normal values.
  2. If the temperature is normal then open the hood and look for abnormal noises in the engine. If you hear any unusual sound then kill the engine.
  3. Assuming everything is normal (temperature and sounds) go around to the back of your car to check for signs of problems from the exhaust. Any gas smell, rotten eggs smell or blue, white or black smoke is a bad sign. Shut off the engine if necessary.
  4. Last but not least, call your mechanic. Inform him of your findings. A professional will always know what to do. Be prepared to tow your vehicle if your mechanic says to do so as driving it may cause more damage.

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