Check Engine Light On But Car Runs Fine – Causes and Solutions

You’re running pretty late on a Monday morning. You crank up the car just to have a “check engine light” blinking in your face. You wonder if it is something that should be taken to your mechanic right away, or can it hold a while.

We all have been guilty of driving the car around for weeks or even months with our CEL on. How do we know if it’s something that requires our immediate attention or just something minor like the low level of wiper fluid?

Sometimes the engine light may come on right after fueling when the gas cap is a bit loose. It can also mean that your catalytic converter should be inspected. Either way, it’s never a good idea to ignore the issue as it could cause severe problems.

So, without any further ado, let’s have a look below to have complete information about what you should do if your car engine light is on, even when the car is running fine.

Check Engine Light On But Car Runs Fine

If the check engine light (CEL) is on, then there is something wrong. It can be either complex or simple. Since there has been no clear change in the operation of the car, it is something quite simple.

The car may have issues like a loose tank cap or even a broken one, unchanged oil for a long time, presence of air in the gas, washing the engine lately, etc. Below is the explanation of these main reasons for the check engine light to come on, but at the same time, the car runs fine.

Your car can have quite a loose gas tank cap, and there is also a possibility of this tank breakage. It could be literally anything. So, reading code is the best way to check as it will instantly tell the main reason.

If the oil has not been changed for a long time the CEL can also come. Failure of the O2 sensor can also lead to CEL. Plus, the presence of air in the tank will also cause CEL. You can buy a new O2 sensor from Amazon.

Another possibility is if you usually wash the engine lately, it will set off the CEL. In addition, if the car is missing the CAT, it will surely throw CEL.

CEL is also turned on by ECU for EMISSION reasons strictly. It doesn’t come on for various reasons including mechanical issues unless they’re affecting the engine emissions directly.

Check Engine Light Comes On And Off

Check engine light is a part of the warning system of obd2 in your car. You are driving the car and the light comes on, the computer will tell you if there is an issue in the car or not.

If the light of the engine flashes on and off, it clearly means there is a serious issue, and you should instantly get it checked right away.

If it is on, then there can be an issue due to numerous reasons that you can see on the owner’s manual. It could be something as simple as the gas cap is loose. Plus, it can be something as expensive as needing a quite new catalytic converter.

The computer runs a bunch of tests constantly on your car’s system. It is an endless testing system to examine if anything wrong happens or not. If the light comes on while driving, but later it turns off itself,

For instance, if you have put in the weak gas, the CEL will turn on unless you refill it. It means that the computer system of your car is extremely sensitive that it can even collect little imperfections & warn you about them on the spot.

If CEL comes on, then goes off, don’t worry about it as long as the car runs okay, because, in our modern computer-controlled vehicle, these are just computer glitches.

Check Engine Light Came On While Driving

There could be many things that can cause the check engine light to come on while driving. It can be a pending code stored in the computer. Plus, it can also be the frozen electronic stability control sensor, a loosened gas cap, or the clogged air filter.

Humidity may cause ignition issues that might set a specific code. Similarly, faulty O2, wiring issues, and vacuum leakage can also lead to the check engine light on. Are you worried about how can you beat that? No issues!

For a perfect solution, you can simply unplug the ECU fuse for around 5 minutes and then put it back in. After that, if it still comes back, just look at more possibilities, or you can also read the codes.

There is a breather valve on the top side of the fuel tank in order to prevent forming the vacuum, which may be blocked completely with mud or dirt. Clean the breather valve & reset the ECU simply by disconnecting the batteries for about 20 minutes, or you can also pull the IGN/ECU fuse.

It is very difficult to diagnose such an issue, but yes check engine light should not be taken lightly especially if there is a power loss.

Check Engine Light Went Off After a Week

Are you facing an intermittent issue? Is the ECM sensing something really wrong, like an issue with the valve control system or a tiny evap leak? If yes, just get a scanner for pulling the code history up. It will keep the codes track even if they’re not currently set as a hard code.

The light may keep coming on and stay on unless you fix the issue. It could either be a harmful misfire from a coil or an occasional breakdown. It can also be a specific code in the computer.

Let’s say at some point the car has passed the tests 3 times. Thus, whatever tests have failed and turned the engine light off, but these codes will remain on your computer. After around 40 tests, the code will go away from your computer with the CEL.

Therefore, light can go on and off depending entirely on the failing and passing of computer tests. In this condition, the CEL isn’t static. Rather, it is quite intermittent.

What To Do When Check Engine Light Comes On?

Your car’s digital system is constantly monitoring what is going on. When it detects the issue, it instantly turns on the CEL. There are unlimited possible codes, so you’ve to determine which code is stored in your computer.

Unplug the minus power code from the battery for approximately 1 minute. It resets the car computer system. After that check again whether CEL blink or not. If your check engine light is flashing on and off, either get the car towed to a professional mechanic or drive it to the nearest mechanic.

For that purpose, you need a specific scan tool that you’ll plug into the dash. After that, get the key and simply put it in the ignition. Turn it to the on position, and choose the function of recording, and then push enter. As a result, it will tell you what codes it has. See the latest price here.

What Could Cause The Check Engine Light To Come On?

Possible causes of the check engine light to come on are:

  • Defective Oxygen Sensor
  • Mass Airflow Sensor(MAF) needs replacement
  • Fuel Economy
  • Spark Plugs/Plug Wires are Faulty
  • Damaged/Loose Gas Cap
  • Failing Ignition Coil
  • Bad or Faulty Catalytic Converter

Defective Oxygen Sensor

Oxygen Sensor sends the measured quantity of oxygen to the computer, which results in adjusting the engine’s air as well as a fuel mixture. In addition, whenever the sensor gets damaged, you’ll surely utilize more fuel than needed.

Want to know why? The defective oxygen sensor may consume all the fuel in a covered distance of just a few miles. Plus, it can damage the catalytic converter and spark plugs, too. Hence check engine light will be on.

Mass Airflow Sensor(MAF) needs replacement

Mass Airflow Sensor is specifically designed to determine the quantity of fuel that is required on the spot. It is entirely based on how much air is entering the engine so the efficiency can be maintained for a long time.

Either the sensor is not installed correctly or the air filter is dirty, they will surely cause the failure of this mass airflow sensor. Furthermore, if your car has any issues or defects, the car engine light will be turned on automatically.

Poor Fuel Economy

Defective or damaged MAF sensors can cause a great compensation to the Oxygen sensor, spark plugs, or catalytic converter. The air intake of your car is highly technical. Thus, the poor fuel economy is a major cause of CEL.

Spark Plugs/Plug Wires are Faulty

Worn wires and plugs can block the converter completely, which can lead to much damage to the oxygen sensors as well as ignition coils.

At this time, you’ll surely notice that all these issues are somehow linked with each other. Therefore, make sure that you are not ignoring such little problems that can cause major issues in the future.

Damaged/Loose Gas Cap

A loose, missing, or damaged gas cap can cause your CEL to appear and there is a reason behind that. A gas cap entirely seals the fuel system & maintains the pressure at the same time.

It might be that your fuel system has a particular vapor leak. It can also be a serious or a minor issue depending on what portion of the system is defective.

Failing Ignition Coil

The ignition coil is the main part of the ignition system of your car. It is responsible for producing the engine spark. As it affects the engine directly, any issue like shorts or burns may cause your CEL to come on.

Bad or Faulty Catalytic Converter

A catalytic converter converts extremely dangerous gases like carbon monoxide into carbon dioxide, which isn’t safe for you. It controls your car’s emissions and makes it eco-friendly to a great extent. And guess what? You can’t even pass the emission test if you’re constantly ignoring this defect in your car.

Just don’t drive anymore with this issue as it can make the condition of your car even worse. It is a famous proverb that “Prevention is better than cure”. So, just don’t let down this issue and save your car from further damage.

Product You May Need

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Now that you are entirely armed with more troubleshooting tactics and knowledge. Ask yourself if it is safe to drive the car with the CEL on? If you have read all the troubleshooting techniques I have outlined, then yes, you should definitely head home.

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