The Most Common Check Engine Light Causes

When Check Engine Light illuminates on the dashboard, it could be a minor issue, like a faulty gas cap, or it could be something more serious, like a misfiring engine. Don’t ignore that warning light. Otherwise, you can end up with a costly repair.

If the check engine light illuminates, it will either blink or remain constantly illuminated, depending on the problem. A blinking light, or in some cars a red light instead of a yellow or orange light, indicates a problem that needs immediate attention. If the light is blinking, pull over, turn the car off, and call for assistance. A steady light means there’s no immediate cause for alarm, but you should still get it checked out.

The Check Engine Light is part of your car’s onboard diagnostics system. When there is a problem in the electronic control system that it can’t correct, a computer turns on a yellow warning indicator “check engine,” “service engine soon,” or “check powertrain.” Mechanics use an electronic scan tool or a diagnostic computer that identifies the source of the problem. You can also purchase your own OBD II code reader.

This code will just point you in the direction of the problem, but anyway you will need an experienced professional to diagnose and repair the issue.

Here are the 10 most common problems that can illuminate the Check Engine Light.

1. Oxygen Sensor Failure

The oxygen sensor measures the amount of unburnt oxygen in car’s exhaust system. It helps monitor how much fuel is burned. A faulty sensor will send incorrect data to the computer and cause a decrease in gas mileage. A car will keep running even if an O2 sensor needs to be replaced, but it will burn more fuel than usual. A bad O2 sensor can lead to damages of the components such as spark plugs and the catalytic converter. It may also cause a car to fail an emissions test. Replacing an oxygen sensor is very easy. Check the owner’s manual for more info. If you know where the sensor is located, you only have to unclip the old sensor and replace it with a new one.

2. Loose or a Faulty Gas Gap

It is one of the most common reasons why the Check Engine Light comes up. The cap is a vital part of car’s fuel-delivery system. If it becomes cracked or loose, fuel vapors leak out and can throw the whole fuel system off. As soon as you notice this warning light, first of all, check the gas cap. Pull over, tighten it, and check for any cracks in it. Continue driving and see if the Check Engine Light turns off. Sometimes the cap needs to be replaced, and you can purchase a gas cap for a few dollars online or at any auto parts store. Replace it on time if you want to improve gas mileage. Just take the old one off and screw on the new one.

3. Catalytic Converter Failure

The catalytic converter reduces exhaust gases. It converts carbon monoxide and other harmful materials into harmless compounds. A failed catalytic converter decreases your vehicle’s gas mileage and performance. Regular maintenance can help you to keep the catalytic converter in working condition. Otherwise, a new catalytic converter is quite expensive, and you can’t do it yourself. You need an experienced mechanic to fix the problem.

4. Spark Plug, Ignition Coil Issue

An ignition coil generates the electricity the spark plug s need to ignite the fuel and air mixture in the cylinders. A malfunctioning coil will cause the Check Engine Light, and if your car burns diesel, then most probably the problem is in the ignition coils.
Worn out or failed spark plugs can cause an engine misfire and heavy acceleration. Since this is part of your vehicles regular maintenance, most spark plugs should be replaced every 25,000-30,000 miles. Newer ones can last up to 100,000 miles. Replace them right away. It’s easy and cheap, and your car will run better.

5. Bad Spark Plug Wires

A spark plug wire transfers electricity from the coil to the spark plug. Without it, the fuel and air mixture in the cylinders wouldn’t ignite. Most vehicles use a single wire per cylinder, but cars with two spark plugs per cylinder use two wires.
If the spark plug wires get damaged, you will notice a rough idle, a bad engine performance, and lower gas mileage.

6. Mass Airflow Sensor Failure

The mass airflow (MAF) sensor monitors how much air enters the engine. Symptoms of a MAF failure include a rough idle, trouble starting, reduced gas mileage and stalling.
Most mass airflow sensors fail because of an improperly installed or old air filter. The air filter should be replaced at least once a year if you want to prevent the airflow sensor from failing.
Replacing the MAF is not so difficult to do on your own, but it is better if you go to your mechanic to ensure that it is installed properly.

7. Vacuum Leak

Every car is equipped with a vacuum system that performs a wide variety of functions. The brake booster is vacuum-operated, and the vacuum system also helps lower harmful emissions by routing the fumes as gasoline evaporates through the engine. If you noticed a surge idle at high rpm, a vacuum leak could be the issue.
One of the most common causes of vacuum leaks are dried out or cracked hoses , due to intense heat or extreme cold circumstances. Other common problems include cracked fittings and loose connections. Replacing the vacuum lines is easy and cheap enough, but determining the leak can take a lot of time.

8. Exhaust Gas Recirculation Valve Failure

The exhaust gas recirculation (EGR) system decreases the amount of nitrogen oxide that comes out of the car’s engine and increases the vehicle’s performance. It directs the hot exhaust gases back into the combustion chambers, which warms up the fuel and makes it easier to burn. It also reduces emissions. The EGR valve can get clogged up or fail. Sometimes it is enough to remove the valve, to clean it up and reinstall it. But if it needs to be replaced, contact a certified mechanic.

9. Dead Battery

The battery is an essential part for starting your car, to light up the road or even to charge your phone. Today’s batteries last much longer than before, and they’re maintenance-free. The price depends on your vehicle’s make and model. Changing or charging a battery is easy, but in some newer car models, it might be a little difficult to access. Before disconnecting the battery, ask your local dealer for the code for the stereo system. Otherwise, you’ll not be able to listen to music or will need another radio.

10. Aftermarket Alarm Issue

If an aftermarket alarm is not installed properly, it can drain the battery, illuminate the Check Engine Light, or even prevent the vehicle from starting.
If you are experiencing one of these issues, reinstall, or replace the aftermarket alarm entirely by a mechanic to solve the problem.

In short, don’t wait until the Check Engine Light comes on to repair your car. Maintain your vehicle regularly, if something needs to be replaced, get it replaced right away.


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