Why is the check engine light on when my car runs fine?
The check engine light on your dashboard has come on, but your car doesn’t seem to run any differently than normal. What do you do now? If your car isn’t running properly, you may want to stop and have it inspected.
On the other hand, if your car is running fine even when the check engine light is on, you may want to keep driving. This guide will explain the main causes of this condition. It will also show you how to fix the problem and provide helpful answers to your questions.
Why is my check engine light on but my car won’t run properly?
Your fuel cap could be loose or leaking. It could also be an intermittent problem, a faulty oxygen sensor, or a dirty MAF sensor. If not, you could have an intake vacuum leak, a bad catalytic converter, bad spark plugs, a faulty ignition coil, a faulty battery or alternator, or even an electrical problem. By evaluating your options, you may be able to determine what is wrong with your vehicle.
1. Loose or Leaking Fuel Cap
One of the most common issues that will cause the Check Engine Light to come on without any other symptoms is the fuel cap. The fuel cap is necessary to seal in fuel vapors and prevent contaminants from getting into the system. If the fuel cap is cracked or missing, the system will not be able to produce normal pressure, which will cause a code to be issued.
Additionally, refueling the tank while the engine is running can trip the pressure sensor in the fuel tank and cause the computer to think there is a leak in the EVAP system. For this reason, it is a good idea to turn off the engine before opening the fuel tank cap.
2. Intermittent Problems
You may have had a problem but not noticed it because it didn’t last long. For example, if the oil pressure is too low for some reason, it can turn on the check engine light. It could also be that the engine is being overstrained when towing.
If the transmission was slipping slightly, you may not have felt it, but a code may have been set. There are many different issues that could be causing the problem without you knowing, which is why we need to run our diagnostic procedures to find out what’s wrong.
3. Faulty Oxygen Sensor
The oxygen sensor is part of the emission control system. These sensors are needed to detect the amount of oxygen in the exhaust gases. If the levels are low, a message is sent to the computer to adjust the air-fuel ratio. If a sensor is faulty and gives an erroneous reading, the Check Engine Light will come on.
Oxygen sensor failure may not have any symptoms at all. In some cases, engine performance may decrease depending on how much the air-fuel ratio is adjusted.
4. The MAF sensor is dirty or faulty
The mass air flow sensor (MAF) sits between the intake manifold and the air filter. It measures the amount of air entering the engine, but the computer makes the same adjustments as the oxygen sensor. If the airflow measurement is incorrect, the computer will make various adjustments to compensate for this.
However, if this sensor fails or becomes contaminated, it can cause erroneous readings and turn on the Check Engine Light. Some engines use a manifold pressure (MAP) sensor instead. In either case, these sensors can fail and cause problems.
5. Suction Vacuum Leaks
Vacuum leaks allow air to be sucked into the engine from places other than where it shouldn’t be. In some cases, these leaks are so minimal that they don’t cause any symptoms. However, if the leak gets worse, you will experience performance issues. If the engine runs lean, you may experience vibrations or misfires.
6. Faulty Catalyst
A catalyst is needed to convert toxic gases that come out of the exhaust into less harmful substances. However, catalytic converters can become damaged or clogged over time. This most commonly occurs when maintenance isn’t performed regularly, leaving unburned fuel in the exhaust.
If your catalytic converter fails, you may not notice any symptoms at first other than the Check Engine Light. Your car may also not pass emissions testing until it is repaired.
7. Faulty Spark Plugs or Ignition Coils
The ignition system includes both the spark plugs and the ignition coils. Both parts wear out over time. However, you may not be fully aware at first of what is happening when a problem occurs and your Check Engine Light comes on.
But when spark plugs or ignition coils go bad, you will experience serious performance issues. Misfires often occur in cylinders with defective spark plugs or coils.
8. Battery or Alternator Failure
You need a functioning battery to start your car. The alternator is the main component that charges your car’s battery while the engine is running.
If any of these components are faulty, it can cause the Check Engine Light to come on. This may also cause the battery light to come on. However, if there’s a problem charging, you’ll soon see symptoms like: Your car may no longer start or your headlights may be dim, for example. 9. Electrical Problems
Your car has cables running under the hood and all over the dashboard. These cables connect all the sensors and components. If one of the cables is worn out or has a bad connection, it will cause a short circuit.
These electrical problems can cause your Check Engine Light to come on. However, you may not notice symptoms of a problem until you need the component.
What to do if the check engine light comes on when your car is running fine
You might be tempted to ignore the problem since your car is running fine, but that’s not a good idea. Ignoring the situation will only lead to bigger problems. Plus, if something else breaks down, you won’t know what’s wrong with your car because the light will already be on. That’s why we recommend following these steps to help you figure out what’s wrong:
1. Place Reading Error Codes
The Check Engine Light comes on because the system issues a code that indicates a problem. To read these trouble codes, you need to get a compatible scanner and plug it into the OBD-II port located on the left or right side under the steering wheel.
Some problems will cause a generic error code to appear. For example, if your EVAP system has a leak because of a loose fuel cap, you may see trouble code P1450.
2. Researching Error Codes
Probably, the error code itself doesn’t tell us anything. Even as professional mechanics, we only know some of the most common error codes. For the rest of you, we have to do the research.
To make it easier for you, we’ve put together some of the most common DTCs in one place. With our error code library, you’ll get the definition, cause, and possible solutions for most issues. If there are multiple codes, you can easily figure out the problem by combining them.
3. Fix the problem (if found)
Once you’ve discovered the problem, you can now fix it. Some problems are easier to solve than others. For example, tightening a fuel cap doesn’t take much time, but replacing spark plugs takes a bit more effort. Additionally, there is a cost associated with each repair. Here are some cost estimates to consider:
New gas cap – $5 to $35
Oxygen sensor replacement – ​​$65 to $450
Mass air flow sensor replacement – ​​$75 to $550
Intake vacuum leak repair – $50 to $600
Catalytic converter replacement – ​​$900 to $1,500
Spark plug replacement – ​​$50 to $450
Ignition coil replacement – ​​$150 to $350
Car battery replacement – ​​$125 to $400
Alternator replacement – ​​$250 to $750
Electrical connection repair – $50 to $550
If you can do the work yourself, you can save a lot of money.
4. Reset the codes and take a test drive
Once the problem is fixed, you should reset the codes using a compatible scanner. The code will not reset automatically, so the Check Engine Light will remain on.
After turning off the light, test drive the vehicle to make sure the light stays off. If it turns on again, there may be another problem that you overlooked.
5. Consult a Professional
You can contact a professional at any time during this process. If you don’t know the error code, can’t find the problem, or you’re not confident that you can fix it yourself, your best bet is to take it to a mechanic.
If you don’t currently have a relationship with an auto repair shop, it may be hard to know who you can trust. For this reason, we recommend consulting with friends and family about who to hire.
Has your car’s check engine light ever come on erroneously?
It’s possible that a sensor gave a false reading, but the problem was just coincidence. If resetting the codes works, the light will stay off.
Does the check engine light mean nothing? The check engine light may have come on due to an incorrect reading from a sensor. In this case, resetting the light will not make it come on again. A faulty fuel cap could also cause the light to come on, but this is an easy fix.
Will putting the gas cap back on turn off the check engine light?
If the light is on because of a loose or broken gas cap, retightening or replacing the gas cap should fix the problem. However, the light won’t go off on its own. In some cars the light will reset automatically if you drive for a few minutes, while in others you may need to use a diagnostic tool to reset it.
What resets the check engine light?
The easiest way to reset the check engine light is with a compatible code scanner. Alternatively, you can remove the car battery for a few minutes, but this will also reset the stereo and seat memory. Driving for a while may also reset the light, but this doesn’t work often.
The check engine light causes panic for all drivers. It should sound an alarm, but there’s no need to worry. With the right code scanner, you’ll always know exactly where the problem is with your vehicle.
Immediate attention can help you fix the problem before you even notice the symptoms. Address the problem while your car is still running smoothly, reducing downtime.
