1. It’s Time To Replace Your Oxygen Sensor
Oxygen sensors are a common cause of “check engine” lights. This sensor is located in the emission control system of your car, and is standard on all vehicles manufactured after 1980. The oxygen sensors are used to ensure that your engine is burning the correct amount of fuel, and running at peak performance. It also works with your catalytic converter to keep your emissions in check.

Over time, the oxygen sensor or O2 sensor can get covered in oil ash. This will reduce its ability to monitor the fuel (fuel system) and oxygen mix in your engine, and it will malfunction (can cause the check engine light to illuminate). Plus, it can also damage the air conditioning system.

2. your Gas Cap Is Loose Or Faulty
Sometimes this is all it takes to illuminate your “check engine” light. It may seem silly, but a loose gas cap (or damaged gas caps) totally throws off your vehicle’s emissions systems, because fuel vapors will leak out of the gas tank. This can lead to decreased vehicle efficiency.

The fix for this problem is very simple. Just check your gas cap! Is it loose? Tighten it up, and see if your “check engine” light turns off!

If your gas cap is damaged, that’s not a problem. Head to an auto parts store, and you should be able to purchase a replacement for $5-10.

3. Your Catalytic Converter Is Failing
Catalytic converters are responsible for reducing the emissions of your vehicle by converting carbon monoxide and other dangerous gases into harmless compounds. Most catalytic converters are good for the entire lifetime of your car – they typically last over 300,000 kilometers.

However, it’s possible that your catalytic converter is the source of your problems. If you’ve noticed deteriorated fuel efficiency, strange smells, and decreased performance, you may want to get your catalytic converter inspected.

Unfortunately, the fix isn’t cheap. Most catalytic converters cost upwards of $2,000, and you’re not going to be able to replace it yourself unless you’re an experienced mechanic.

4. Mass Airflow Sensor Needs Replacement
If you don’t regularly service your car’s air filter, you could be putting your mass airflow sensor at risk (and your exhaust system). This sensor helps your car’s computer inject the proper amount of fuel into the engine, increasing performance and efficiency.

If you don’t replace your air filter, this mass air-flow sensor can start to malfunction and provide incorrect information – leading to poor gas mileage, car stalling, and increased emissions. Because of this, you should replace your car’s air filter at least once a year.

The fix is pretty simple – but can be a bit expensive. The average cost of a mass airflow sensor is around $200. It’s best to let a mechanic perform auto repairs, and to consider replacing air filters while you’re still in the shop. This will ensure your new mass airflow sensor lasts for the years to come.

5. Faulty Spark Plugs
Spark plugs can last anywhere between 75,000-200,000 kilometers, depending on when your vehicle was manufactured. Spark plugs seal your combustion chamber, and provide the spark that ignites the fuel in your vehicle’s engine (ignition system).

If you have a bad spark plug or your spark plug wires start to misfire (ignition system issues), your check engine warning light will certainly turn on, and you may feel a “jolting” sensation when you try to accelerate your car.

The good news? Spark plugs are insanely cheap – and easy to replace. You can usually purchase spark plugs for about $10 a piece, and you can usually replace your old spark plugs on your own. Check out this handy video guide to learn how to replace spark plugs!

Don’t Panic When Your Check Engine Light Comes On!
These above 5 issues are responsible for the vast majority of check engine light comes on occurrences. So next time your check engine light comes on, don’t panic. The check engine light means something, but it could be nothing at all, or one of these simple issues.

However, you shouldn’t just start replacing parts without diagnosing your issue. You can purchase a code reader if you want to diagnose your car’s issue yourself, or you can just head to your nearest auto shop for a tuneup and an analysis.