We’re going to say this from the start: if your check engine light is flashing, stop your car immediately. A check engine light flashing means there’s a major issue with your car and you should stop driving. Continuing to drive might cause even more damage to your car. Now that you’ve stopped your car, we’ll be explaining how the check engine light works, what problems it might indicate as well as what causes it, and possible repair costs you could be looking at.
Understanding the Check Engine Light
A check engine light or CEL is a warning system that your car uses to warn you when there’s an issue with the car. A CEL usually indicates there’s something wrong with your engine. The problem may range from a dirty fuel tank to a bad catalytic converter. There are three ways your check engine light could illuminate, which are: continuously lit, intermittent illumination, and flashing or blinking. The way your check engine light illuminates indicates the severity of the issue, here’s what it could mean:
1. Continuously Lit
If your check engine light turns on and it stays continuously lit, then it usually means there’s a minor issue with your engine. As mentioned, this may indicate a variety of issues, but it’s usually not too bad and should be fairly cheap to fix. In fact, something as simple as a loose gas cap can trigger the check engine light to turn on. Some other common issues include a faulty spark plug, a bad ignition coil, or dirty fuel injectors.
You will probably still be able to drive your car in relative safety. However, we still recommend taking your car to a repair shop and diagnose the problem before it gets worse.
2. Intermittent Illumination
This is when your check engine light turns on, then turns off, but then turns on again after a while. This usually indicates a sensor problem with the engine. You might also experience intermittent misfiring with your engine, which could indicate a failing ignition system. You should still be able to safely drive your car when this happens. But again, we recommend diagnosing and fixing the problem as soon as possible.
3. Check Engine Light Flashing or Blinking
As mentioned, you should immediately stop driving if your check engine light is flashing. This indicates there’s a serious issue with your engine, and it would be unsafe to keep driving. Ignoring a flashing check engine light will lead to even more severe damage and costly repairs.
Additionally, a flashing check engine light is usually accompanied by a misfiring engine. The reason that it’s flashing is that the misfiring is so bad that it could soon cause damage to major components such as the catalytic converter. If your engine is misfiring, it would be uncomfortable to drive anyway and your car might die soon. Best to stop driving and call a tow truck to the nearest repair shop.
What is an Engine Misfire?
If you see a check engine light flashing, you will often experience misfiring in your engine. As previously explained, when a CEL is flashing instead of continuously lit, that means the misfiring or the problem is urgent and can cause further serious damage to major components in the car. But what is an engine misfire?
Well, your engine contains several cylinders where the combustion process happens. This combustion process is what powers your piston to move, which ultimately powers your car to move. When one or more cylinders fails or aren’t firing, your engine’s synchronization will be disrupted causing your engine to run roughly. This affects several things including performance, fuel consumption, and emissions. If emissions are affected, then it could cause damage to your catalytic converter, leading to some very expensive repairs.
If you want to learn more about how a car engine works, watch the video below:
Symptoms of a Misfiring Engine
A check engine light flashing is often accompanied by a misfiring engine. If you’re not sure whether your engine is misfiring or not, here are some symptoms to look out for:
1. Engine Sound
A car’s engine is designed to run smoothly, if misfiring occurs, then you will notice your engine sounds “off”. What we mean is that the engine doesn’t sound smooth and in severe cases, you will notice your engine sputtering. In which case, you will likely notice the next symptom:
2. Rough Idle or Jerking While Accelerating
When an engine misfires, you will likely notice that your engine is running rough. During acceleration, your car may even jerk as one or more cylinder isn’t firing correctly. It usually feels like your car is hesitating, and the RPM usually stops climbing for a moment, and then continue climbing a moment later.
3. Loss of Power
Since your engine isn’t firing correctly, you will notice a loss of power. As mentioned, misfiring interrupts the “rhythm” your engine has which affects the amount of power your engine can produce. Your engine will often struggle to climb above 3,500 rpm, making it unable to deliver full power.
4. A smell of Gas
If you smell gas then it might indicate a leak in your car’s fuel system. Misfiring can also result in a gas smell inside your car. This is usually because your car is unable to burn fuel properly, resulting in the smell of unburnt gas in your car. This can be caused by either a faulty ignition system or too much fuel being injected into your engine.
5. Difficulty Starting the Engine
As mentioned, a misfiring engine is caused by one or more cylinders that isn’t firing properly. When one or more of your cylinders isn’t working, you will often find it difficult to start the car. If you see the symptoms above and you struggle to turn on your car, then you could have a misfiring engine.
Possible Causes and Repairs for a Check Engine Light Flashing
As mentioned, a flashing check engine light is caused by a significant problem in your engine that could lead to serious damage to other major components in the car. Here are 10 common causes for a flashing check engine light, as well as the possible repair cost you could be facing:
1. Bad Oxygen Sensors
One of the most common causes for a check engine light flashing is a bad oxygen sensor. This sensor is responsible for monitoring the oxygen level in your car’s exhaust system. This information is then used to determine the fuel and air mixture ratio that should be put into your engine. When this sensor goes bad, your engine will receive an incorrect mixture leading to misfires. And as explained previously, misfiring can lead to costly damages to other major components.
An oxygen sensor typically costs between $120 – $480 to replace including the labor cost. However, if you want to do it yourself then the part itself should cost you no more than $100 to buy.
2. Bad Spark Plugs
This is also quite common but very simple to fix. A spark plug, as the name suggests, is used to create a spark in your engine’s cylinder. This spark is used to ignite the fuel and air mixture in your cylinder, which is needed to power your car. Spark plugs are usually changed by your mechanic around every 10,000 miles. So, if your car is maintained properly, you shouldn’t have a problem with this. But keep in mind that if your spark plug fails prematurely, then there could be an underlying issue with your car. Such as too much fuel being injected or a head gasket leak.
Most of the time, bad spark plugs won’t lead to a flashing check engine light and it will usually just lit continuously. However, if the misfiring gets bad then your check engine light might flash, indicating that the misfiring has gotten bad enough that it could cause severe damage.
In any case, if you need your spark plugs changed then you can rest easy since it isn’t too costly. At the very most you will pay $250 for a spark plug replacement job. However, you can save some money and change them yourself as it’s relatively easy to do. The spark plug itself can be as cheap as $10 each.
3. Faulty Ignition Coils
The ignition coil is responsible for sending high voltage electricity to your spark plugs and power them. If your ignition coil has gone bad, then it won’t be able to send enough power to the spark plugs. Thus making the spark plugs unable to create enough spark to ignite the fuel and air mixture in your engine.
There are several tests that you can do to diagnose an ignition coil, such as using a spark tester. In any case, if you do need to change your ignition coil, then the cost will vary. This depends on what car you have and the type of ignition coil it uses. However, most modern cars use a pencil coil or coil-on-plug system. If your car has this, then it will cost you between $150 – $300 to replace an entire set of ignition coils. With labor, your total could be as high as $450.
4. Bad Ignition Cables or Wires
Unlike coil-on-plug systems, a distributor-type coil sits remotely from the spark plugs and connects via cables instead. This cable can go bad sometimes due to heat, physical damage, or just general wear. When it does fail, you will need to replace the cables. Otherwise, the ignition system won’t work properly.
Thankfully, they aren’t too expensive to replace. They typically cost between $80 – $300 for an entire set of cables, depending on your car’s make and model. If only one of your cable has gone bad, you could buy them individual cables rather than an entire set to save some money.
5. Bad Timing Belt
A timing belt is responsible for synchronizing your engine’s functions. The belt controls the rotation of the crankshaft as well as the camshaft, along with the opening and closing of the engine’s valves. Keep in mind that the check engine light won’t come on because of the timing belt itself, but usually because of a misfire caused by an incorrect valve opening.
The timing belt is crucial for your engine’s operation, and will usually last for about 60,000 to 100,000 miles. You should be able to check this in your owner’s manual. If you need the timing belt replaced, then it will usually cost between $500 -$900. It’s quite expensive, but we recommend you replace it immediately as a bad timing belt can cause further damage to other components. These components include the pistons, valves, and water pump, which are monumentally expensive to fix.
6. Clogged Fuel Filter
A fuel filter’s job is to filter rust and dirt out of the fuel before it’s injected into your engine. They usually sit somewhere in the engine bay and are often cylindrical in shape which contains the filter paper. When the fuel filter clogs up, your fuel system won’t be able to send the necessary amount of fuel to the injectors and then to your engine. When your engine isn’t getting the fuel it needs, misfiring may occur. Which then leads to the check engine light.
You will normally need to replace your fuel filter every two years or around 24,000 miles. Although the fuel filter in some cars can go as far as 50,000 without needing a replacement. In any case, if you need to replace it then the average cost is about $200 for most cars. However, it could be anywhere between $150 – $700 depending on your car make and model.
7. Dirty Fuel Injectors
Much like clogged fuel filters, dirty fuel injectors would also prevent your engine from getting the necessary amount of fuel. As a result, your engine will misfire. You can clean dirty fuel injectors and don’t have to replace them. However, it will set you back around $100 to have a repair shop clean your fuel injectors.
You can learn to clean your fuel injectors yourself to save money, the most basic cleaning method simply requires you to add a cleaning fluid into a nearly empty fuel tank. Other methods will require tools and basic mechanical knowledge to do it.
8. Faulty Mass Air Flow (MAF) Sensor
Your engine needs to take in air to ignite the fuel and start the combustion process in the engine. To be able to take in the correct amount of air, your car uses a mass airflow (MAF) sensor to tell your ECU how much air to put into the engine. If the sensor is faulty, then it may take too little or too much air, causing the car to misfire. In severe cases, the car may even suddenly shut off. It usually costs around $150 to replace a MAF sensor.
9. Bad Catalytic Converter
Most of the problems above don’t always trigger a flashing check engine light unless they have gotten really bad. However, when your car’s catalytic converter goes bad then you will likely see that dreaded amber light flashing on your dashboard. The catalytic converter is responsible for reducing the toxic and harmful gases and pollutants that your car produces. When it fails, it won’t be able to do so. It can also affect the airflow in your exhaust system which then causes your engine to burn extra fuel. You will notice a loss of power and increased fuel consumption when this happens.
Most of the time, your car can go for up to 10 years without a new catalytic converter. However, the problems we mentioned above can lead to excess emissions, which can shorten the life of the catalytic converter. The replacement cost for a catalytic converter can be as high as $2500. This is why we recommend taking care of any issue before it damages your catalytic converter.
10. Gasket Leak
A head gasket leak won’t trigger your check engine light to turn on per se, but the effects of it will. A head gasket connects your engine block to the cylinder head. It acts as a seal that prevents oil and coolant from entering the engine’s cylinder. When you have a leak, or worse, a blown head gasket, then it won’t be able to seal properly. This will then allow oil and coolant to enter the cylinder, causing a myriad of problems such as misfires and thick smoke coming out of your exhaust. These effects then cause the check engine light to flash.
A gasket leak will affect performance, fuel consumption, as well as emissions. If left unfixed, then it will cause further damage to other components such as the pistons and the catalytic converter. A head gasket set usually costs no more than $200 to purchase, but the total cost to replace it can be as high as $1500. This is because replacing a head gasket is a complicated and labor-intensive process. Basically, your mechanic will need to take apart most of your engine and then rebuild it once the new head gasket is installed.
Diagnosing a Check Engine Light Flashing
Keep in mind that the 10 things we listed above are just some of the common causes. If you want to be sure, then you can diagnose your car’s check engine light yourself at home using an OBD scanner.
What is an OBD Scanner?
Your car has an On-Board Diagnostic system or often referred to as OBD. This system tells you what’s wrong with your car by displaying error codes on the OBD reader when you run a diagnostic. This way, you can immediately tell what’s specifically wrong with your car and proceed to fix it.
Keep in mind that cars made before 1992 will have an OBD-1 system, in which case you will need an OBD-1 scanner. Meanwhile, cars made after 1992 will likely have an OBD-2 system and will require the OBD-2 scanner to read the codes. If you’re trying to do a simple diagnostic test, then you will only need a basic OBD scanner which costs between $20 – $100 to purchase. Be sure to check first which OBD system your car has.
How to Use an OBD Reader
- Plug the reader into the car’s OBD port. This port is often located underneath the dashboard area, either above your pedals or knee. Keep in mind that some cars might have their port hidden out of sight. Check your owner’s manual or online to see where it’s located in your car.
- Once plugged in, turn on the OBD scanner. It should immediately scan the car. However, some scanners might require you to input additional information such as make, model year, VIN number, etc.
- It will then display the error codes it has found. A more complicated scanner might also display a description of what’s wrong with the car, but if you have a simple scanner then it’s recommended to take note of the codes displayed. This way, you can cross-check them with the owner’s manual later on.
- Check what the codes indicate, then proceed with the repair.
If you’re still not sure how to do it, we found a great guide from Car and Driver on how to use an OBD scanner:
Check Engine Light Flashing: In Conclusion…
The most important thing to note here is that, if your check engine light is flashing, then you should stop driving immediately. It would be wise to call a tow truck instead and get your car to the nearest repair shop. Until you can diagnose what the problem is and the severity, it’s best to not drive your car.
Hopefully, your check engine light will only require you to do a simple spark plug or ignition coil replacement (or even a quick reset). Whatever the cause, we recommend that you proceed with the repairs to avoid further and even costlier damage. It’s best to prevent these damages rather than fixing them. That being said, we understand that some repair costs, such as the head gasket and catalytic converter cost might be too high.
If this is the case, then your other only option might be to sell your car in its current condition. This means you will need to sell it below the average market price, but it does mean you won’t have to pay for repairs and it will put cash on your hands instead.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.