What Does A Check Engine Light Mean? (WARNING)

When the “check engine” light in your car comes on, it means there’s a problem that could be small and easily fixed (like installing a new gas cap) or it could mean something more serious.

If the “Check Engine” light is displayed in your car, don’t panic. Take a deep breath and read this guide to help turn the light off and get you on your way as quickly as possible.

What Does A Check Engine Light Mean?

Nearly all cars have an onboard computer, called an engine control unit (ECU). The ECU monitors a vehicle’s internal systems and can display a warning light when an issue is detected. Think of it like the nervous system of your vehicle which is designed to alert you when something is wrong.

It does not necessarily mean that something major is faulty, however, it’s not something you want to ignore for too long. The “Check Engine” light is often misinterpreted by many to indicate catastrophic engine failure when in reality it’s never the case.

Let’s get more detail about the “CHECK ENGINE” light appearing on your dashboard.

What Can Cause A Check Engine Light To Come On?

As mentioned in the beginning there are a few common causes for the “CHECK ENGINE” light to appear. Some of them are more serious than others and require immediate attention, while others can simply be cleared with an OBD-II scanner and repaired at a later date.

A few common causes for the “CHECK ENGINE” light are but not limited to:

1. Catalytic Converter
2. Oxygen Sensor
3. Ignition Coil or Spark Plugs
4. EGR Valves
5. MAF Sensors 
6. Loose Fuel Cap
7. Fuel Injectors
8. Thermostat
9. PCM (Powertrain Control Module) 

These are a few of the most common reasons to make your check engine light come on. Let’s now look at each component in a bit more detail

Catalytic Converter

What is a Catalytic Converter and is it a serious problem? The Catalytic Converter or CAT as they are so commonly referred to is a component located inside the exhaust of the emissions system. Its job is to control and limit toxic gasses generated by the engine from exiting the atmosphere via the exhaust system. It does this by converting the gases and pollutants in the exhaust into water vapor and less harmful gases via a series of chemical reactions.

After years of driving, the catalytic converter becomes clogged up thus causing an error on your dash that says, “CHECK ENGINE”, when in fact it has very little to do with the actual engine.

Can you drive with a bad Catalytic Converter? 

Technically Yes, however, be aware that your vehicle will become sluggish, use more fuel, and emit more harmful gasses while driving with a bad Catalytic Converter. It is not recommended to drive a vehicle with a bad CAT for extended periods.

Oxygen Sensor

Firstly, what is an oxygen sensor? It is a second engine component responsible for controlling the harmful toxic exhaust emissions in vehicles. It is an electronic sensor that measures the residual oxygen content of the exhaust gas and then sends a signal to the ECU. A Bad Oxygen sensor will result in rough idling, poor performance, misfiring, and intermittent stalling. A bad oxygen sensor can disrupt all sorts of essential engine functions and should be attended to ASAP.

Can you drive with a bad Oxygen Sensor? 

No, It is not recommended to drive with a faulty Oxygen Sensor since your engine will use too much fuel, run rich, and clog up the catalytic converter, thus exacerbating the situation. Have it inspected by a reputable repair shop and replaced immediately to prevent further damage. You can use an ODB-II Fault scanner to read and get the error code.

Ignition Coil or Spark Plugs

Any engine that uses a spark ignition system has an ignition coil. Its main job is to convert the 12v battery voltage to a much higher voltage which is required to operate the engine’s spark plugs.  It then takes that high-voltage electricity and uses it to start the vehicle and ignite the air-fuel mixture in the engine’s combustion chamber.

Can you drive with a faulty Ignition Coil?
 Technically, yes you can, however, you can expect poor performance which could also lead to damaging other components. Your catalytic converter is at risk which could lead to extended more expensive damage if left unresolved.

EGR Valves

All modern vehicles have an EGR(Exhaust Gas Recirculation) valve to pass the strict manufacturing emissions tests and lower the vehicle’s carbon dioxide levels. It is a key component in any modern engine which is designed to recirculate fine unburned exhaust gas back into the engine’s combustion system. This is designed to improve the vehicle’s efficiency by reducing fuel consumption and reducing the amount of toxic gases (NOx Emissions) that get sent into the atmosphere via the tailpipe emissions.

Can you drive with a faulty EGR? 

Technically you can drive without a working EGR valve. It won’t affect the health of your engine, however, it will hurt the environment since the evaporative emissions will be more harsh. It can, however, damage your engine if you have EGR fluid from its tiny radiator seeping coolant into your engine’s combustion chamber. Exercise caution since if left unchecked it could result in catastrophic engine damage, especially on diesel engines.

MAF Sensors

MAF stands for Mass AirFlow Sensor and is an air meter that measures the amount of air that is being sent into the combustion chamber of your engine to mix with the fuel. If the MAS is faulty, the signal it sends to the engine will be inaccurate, thus resulting in the “CHECK ENGINE” light appearing.

Without an accurate air reading signal from the mass air flow sensor, the powertrain control module (PCM), which manages the engine, transmission, and other systems in your car, won’t know how much fuel the engine needs.

Can you drive with a faulty Mass Airflow Sensor?

Technically, yes, however, I wouldn’t recommend it.

Loose Gas Cap

Something as basic as a loose gas cap can make your “CHECK ENGINE” light come on. The Fuel cap is the cap located on the outside of your vehicle, usually on the side at the rear and it covers the opening of the fuel tank. If the gas cap is left open or not closed properly, you could spill fuel onto the road and damage the environment.

Can you drive with an open fuel cap? 

Your vehicle will drive, however, it is not recommended. Stop and check and close the cap of the gas tank if possible. You can use an ODB-II scanner to read and clear the fault immediately.

Fuel Injectors

The function of the fuel injectors is to inject a very specific amount of fuel into the engine’s combustion chamber to mix with the air coming in. It is sprayed at a very precise point in the combustion cycle to form the perfect mixture of fuel to air.

Can you drive with Faulty Injectors? 

No, it is not recommended to drive a vehicle with a misfiring engine since it can result in your engine sputtering because of the unequal or unburned fuel, resulting in an unpleasant vibration through the vehicle. This is due to the engine cylinders not all firing as they should. This is unfortunately going to be an expensive repair so brace yourself as injectors are pricey. 

Thermostat

The Thermostat is located in the engine of the vehicle and is responsible for regulating the circulation of engine cooling fluid from the radiator to the engine. This is designed to keep the engine at a safe operating temperature without overheating under most driving conditions and ambient temperatures. If your thermostat fails you can expect a “CHECK ENGINE” light to appear. You can use an ODB-II scanner to read and clear the fault once the thermostat has been replaced.

Should you drive with a faulty Thermostat?

Absolutely, NO! Your vehicle might still be functional, however, if driven the engine will overheat thus causing major damage to the engine and other critical components. Call for a tow truck immediately to prevent further damage. 

PCM (Powertrain Control Module)

A PCM is an acronym for (Power-train Control Module). It is an electronic control unit on your truck consisting of the engine control unit (ECU) and the transmission control unit (TCU). These electronic modules talk to each other, share signals and information, and require the proper voltage to function accurately and reliably.

Can you drive with a faulty PCM?

it is possible to drive your car with a bad PCM, however, further issues can develop that can compromise your safety on the road without any warning.

What Should You Do If The Check Engine Light Is On?

Stop the vehicle immediately and check for any obvious signs. Check that your fuel cap is closed properly then move to the engine bay. Inspect the engine and be on the lookout for any signs of fuel, air, or oil leaks. Also, check the engine for coolant leaks in and around the EGR valve. Look underneath the vehicle and determine if there are any strong fuel smells.

OBD2 Error Code Scanner & Diagnostic Tool

If you have an OBD-II scanner like the one below, check which codes are displayed to give you an idea of where to look. If you do not already own one, join thousands of happy owners, get your OBD2 Scanner here, and forget about costly auto diagnostic tests near you. This is an essential piece of kit for every car owner.

Unlock the power of professional-grade diagnostics without breaking the bank. With our OBD2 Scan Tool, you can perform a comprehensive car diagnostic check in minutes, saving you both time and money. No more guessing games about what’s wrong with your vehicle or overpaying for diagnostics at the mechanic.

How To Fix A Check Engine Light Problem Yourself

Yes, a “CHECK ENGINE” light can be removed if you know which component is faulty and it has been repaired, cleaned, or replaced.

Alternatively, if your vehicle is performing normally and there are no unfamiliar smells or leaks, you can clear the code with an ODB-II scanner and monitor if it reappears. In modern 4WDs and electronic engines with so many sensors, it’s easy for a sensor or something small to cause the “CHECK ENGINE” light to appear on your dashboard.

This should not be taken lightly and further action is required immediately in many cases.

 The consequences of ignoring your “CHECK ENGINE” light can be catastrophic. You should never ignore a blinking warning light or flashing light that says “CHECK ENGINE” or “SERVICE ENGINE”. This is a serious warning that should be, investigated and repaired immediately. If you experience a blinking light or check engine light flashing, stop the vehicle immediately and turn off the engine. 

If your vehicle is experiencing something serious like a loss of oil pressure, catalytic converter failure, or there is a problem with your spark plug wires, then you need to take immediate action. If you are a DIY person, then get out your ODB-II tool to scan for any errors to get an idea of what the problem could be.

Get yourself to the nearest auto parts repair store and resolve the issue immediately. Alternatively, refrain from driving the vehicle any further and contact a tow truck to get your vehicle to the auto repair shop. 

How Can You Find Out The Code?

If you have a CHECK ENGINE code message on your dashboard you will need to run a full diagnostics on the vehicle to establish the cause. The diagnostics scan tool will kick out an engine error code with a description of what the problem is. Armed with this information will give you a better idea of the problem and the possible severity of the situation. 

The Importance of Regular Maintenance to prevent “CHECK ENGINE” errors.

It is important to check your vehicle’s oil, water, and coolant levels regularly. Before embarking on a long trip, take a few minutes to inspect your vehicle’s vacuum hoses, water pipes, fuel lines, and other exposed components for obvious signs of wear or damage.

This can save you thousands in the long run since you will detect an issue before it becomes a major problem.  If there are warning messages or errors appearing on your dashboard gauges attend to it immediately.  

Problem #1: Car Won’t Start

If your vehicle refuses to start there are a few basic checks you can perform to determine the source of the problem. It can be one of 3 things:

1. Air
2. Fuel
3. Electronic

Start with the battery and check its health and age. If you have an OBD2 scanner, plug it in and do a full scan. This tool usually gives you a pretty good idea of where to start looking.

Problem #2: Your “Check Engine” Light Is On

Stop the vehicle and switch off the engine. Plug in an OBD-II scanner to determine the problem. Take note of the code and read the description to get a better idea.

Problem #3: You Smell Gas

Stop the vehicle and switch off the engine. Check the fuel cap to make sure it is closed properly. Look under the hood and inspect for fuel leaks near the injectors. Use an OBD2 fault scanner to determine the problem. Take note of the code and read the description to get a better idea.

Problem #4: Leaks

Stop the vehicle and switch off the engine. Determine where the leak is coming from and if it can be stopped. Determine if it’s a fuel, water, or coolant leak. Do not drive the vehicle until the problem has been identified or resolved.

Problem #5: Worn Spark Plugs

Stop the vehicle and switch off the engine. Replace the spark plugs and clear the “CHECK ENGINE” error with your OBD2 scanner if you have one handy.

Problem #6: Your Thermostat Is Broken

Stop the vehicle and switch off the engine. Do not drive it until the thermostat has been replaced to prevent major damage to the engine.

Problem #7: Your Gas Cap Is Leaking

Stop the vehicle and switch off the engine. Close the gas cap properly or replace the cap.