What does a Check Engine Light mean and what should I do if it comes on?
Every car needs routine maintenance - and proper care of your vehicle puts yourself and your car in the best position to maintain a quality ride throughout the life of the car.
We’ve all been there, going just a couple hundred (maybe even thousand 😱), miles over when that reminder sticker in your car says your vehicle is due for service. Everything is fine until one day that dreaded orange light comes on; the “Check Engine Light”, or CEL as it’s known in the auto repair industry.
The Dreaded Check Engine Light
“Ugh… what’s wrong this time?”
Stress-Free is here to help! The important thing to remember about a Check Engine Light is that it’s one of the most common warning indicators your vehicle dashboard displays, mainly because the CEL covers such a vast array of systems (and system failures). That sinister orange glow could mean the difference between tightening a loose gas/fuel cap, a straightforward repair, or possibly considering a longer-term replacement option for your existing vehicle.
Personal Check-Temperature Light
Unfortunately, there is no simple answer to the question “Why is my Check Engine Light on and what needs to be fixed?”, given how many systems the Check Engine Light covers. Just as vague as the name suggests, there are countless reasons why your Check Engine Light may be on. Imagine if the human body had a Rudolph-the-Red-Nosed-Reindeer feature: Whenever you have a fever, your nose lights up oh-so-bright. There are endless reasons why your personal “Check Temperature Light” might go off - you could have a common cold, be sleep deprived, food poisoning, or something more serious. Your doctor can’t diagnose why your Check Temperature Light is on without gathering additional information, just as your mechanic can’t diagnose your Check Engine Light without having an in-depth look at your vehicle.
Below are the Top 10 most common reasons for a Check Engine Light, including what signs to look for. Our goal is to educate you on how to be best prepared to share any helpful, relevant information with your mechanic, so they can assist in making that CEL go away (and stay away)! If you have an OBD2 reader in your car, we recommend sharing what codes you pulled from the system with your trusted auto repair shop as soon as you can - these codes can provide a high-level understanding of the severity of your issue, but even more importantly, determine if your vehicle is currently in safe driving condition.
CHECK ENGINE LIGHT FAQs
Note: Most codes pulled from a vehicle’s OBD2 reader are generic engine area codes, so pulling the code will not provide an official, informed diagnostic.
Top 10 Common Reasons for “Check Engine Light”
Temperature Warning Light
10. Thermostat
Your car’s thermostat is a device that opens and closes to regulate the temperature of your engine. If this device is stuck open or stuck closed, either could trigger the “Check Engine Light” light to come on.
What to look for - Thermostat Failure: If the thermostat is stuck closed, the vehicle will start to overheat. If left untreated for too long, the overheating will result in your engine to seize. If you notice your vehicle begin to overheat while driving, or if your Temperature Warning Light indicator turns on, we recommend pulling over to a safe spot and having the vehicle towed before serious, irreversible damage occurs.
9. Fuel Injectors
Fuel injectors spray fuel into a car's engine using electronically controlled valves, capable of opening and closing many times a second. If the computers notice that the fuel injectors are adding too much, or too little, fuel to the engine, the Check Engine Light will come on.
What to look for - Fuel Injectors Failure: If your fuel injectors are clogged or starting to defect, you could notice a decrease in fuel economy and a rougher idle.
8. Evap Purge Solenoid
The Evap Purge Solenoid is a part of your Evaporative Emission system. The Evap Purge Solenoid prevents fuel vapors from escaping the fuel tank. Improper functioning of your Evap Purge Solenoid can result in the Check Engine Light coming on.
What to look for - Evap Purge Solenoid Failure: When your Evap Purge Solenoid starts to go bad, you may notice a rougher idle coupled with a lower fuel economy, and it is best to have your vehicle diagnosed for confirmation.
7. Mass Airflow Sensor
As the name of the part says, the Mass Airflow Sensor device measures the amount of air that enters the engine, and is typically located between your car’s intake manifold and air filter.
What to look for - Mass Airflow Sensor Failure: When your Mass Airflow Sensor starts to defect, you can notice anything from rough idle, up to your vehicle failing to start.
6. Evap Purge Control Valve
Another component of your vehicle’s EVAP system, the Evap Purge Control Valve is a device that traps fuel vapors and contains them in a charcoal canister.
What to look for - Evap Purge Control Valve Failure: Some of the symptoms of a faulty Evap Purge Control Valve are a rough idle, as well as the car having difficulty starting, with either triggering the “Check Engine” light.
5. Ignition Coils
An Ignition coil is a component in your vehicle's starting system that draws power from the battery, sends them to the spark plugs, thus creating the spark to ignite the fuel and create combustion needed to properly start your engine.
What to look for - Ignition Coils Failure: Symptoms of an ignition coil going bad can be your car having a slower acceleration, a general feeling of a loss of power when accelerating, as well as a rough idle.
4. Tighten or replace fuel cap
One of the easiest and most cost effective repairs. The fuel cap is an essential part of the vehicle's fuel system, as it seals the system shut. A loose fuel cap could allow oxygen into your vehicle’s system, triggering the Check Engine Light.
What to look for - Fuel Cap Replacement: If your Check Engine Light comes on after filling your tank at the gas station, try tightening the fuel cap and see if the Check Engine Light turns off. If your Check Engine Light remains on, the fuel cap may be loose or have a faulty seal in the cap, at which point will need to be replaced.
3. Catalytic Converter Replacement
The Catalytic Converter takes emissions from the system and filters them through precious metals to ensure your vehicle emissions are released into the atmosphere within a relatively safer threshold.
What to look for - Catalytic Converted Failure: A dead giveaway that your Catalytic Convertor is going bad is if there’s a foul rotten egg-like smell coming from your exhaust. Other signs your catalytic converter may need to be replaced are if you notice darker exhaust smoke, sluggish engine performance, and/or lower car acceleration than normal.
2. Oxygen “O2” Sensor
Tied for first palace here, the Oxygen sensors are little devices that are found throughout your exhaust system, and they regulate the amount of fuel that the engine is using.
What to look for - Oxygen Sensor Failure - Once your O2 Sensors start to become faulty, you could notice a drop in fuel economy, and possibly a rougher idle.
1. Spark Plugs
Flashing Check Engine Light
The number one sign that your car’s spark plugs are the reason your Check Engine Light, is if your Check Engine Light itself starts flashing. What does a flashing Check Engine Light mean? If you notice your CEL continuously flashing, one (or more) of your cylinders is misfiring, and that means it isn’t in sync with the other cylinders in the vehicle. While driving a short distance with a flashing Check Engine Light is possible in an emergency situation, we highly recommend avoiding at all costs due to the compounding amount of damage that can be done to the engine upon further strain.
What to look for - Spark Plugs Failure: Flashing Check Engine Light or very rough idle. Other signs your Spark Plugs need to be replaced are if the engine is sluggish as well as poor vehicle acceleration.
Remember, the Check Engine Light is your vehicle’s way of telling you that it needs to be taken care of, just not what specifically needs to be taken care of. The issues described above are the most common reasons why a CEL warning indicator is present. Every car (including your car) is unique - the vehicle’s year, make, model, maintenance history, driving patterns, and external factors (climate, weather, etc.) - all factor as to what’s resulting in a Check Engine Light. Looking for even more possible reasons? Check out Bumper’s 11 Reasons for the Check Engine Light Comes On.
At Stress-Free Auto Care, our ASE Certified Technicians combine decades of experience with industry-leading tools & equipment to get your Check Engine Light resolved on-time and within budget. Our 24-month / 24,000 mile warranty gives you peace of mind, ensuring your repairs are covered in the event of the unexpected. If your Check Engine Light is on, your friendly team at Stress-Free Auto Care is just a call, text, or email away from giving you the better auto care experience that you deserve.
