Is a Check Engine Light an Indicator of a Serious Problem?

Valerie Raskovic

Apr 23, 2024

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A vehicle check engine light is that ominous glowing symbol on your dashboard. This warning is an indicator that there is something wrong within the drivetrain of the vehicle and often triggers a wave of concern among car owners. But is it always an indication of a serious problem? Let's delve into this common automotive dilemma and shed light on what it might signify.

Let’s start with the basics. Understanding the check engine light may not be very straight forward and often requires the aid of a qualified automotive technician as well as some specialized equipment. However, to give you a bird’s eye view of the possible issues that may be causing the warning to appear on your dashboard display screen/cluster we must first explain how the onboard diagnosis system works.

This vehicle diagnostic system often referred to as OBD2 is prevalent in vehicles made after the year 1995. Vehicles made prior to that year will have an OBD1 diagnostic system. Both systems are engineered to monitors various components and systems such as the vehicle's engine, emissions system, and other critical systems. When the system detects a potential issue that could affect vehicle performance or emissions, it triggers the check engine light to alert the driver. The main difference between OBD2 and OBD1 systems is the amount of data collected and stored as OBD2 have more advanced monitoring systems that may aid in pinpointing the issue more accurately rather than the older and somewhat obsolete OBD1 system.

As you can imagine a check engine lite can indicate a vast number of system failures, so interpreting the cause of the check engine light is a bit tricky and is not recommended for the novice vehicle owner with no automotive knowledge or experience. The challenge for an ordinary car owner, even one who is handy, to diagnose the check engine light in their vehicle stems from the following factors:

Specialized Equipment

One of the most perplexing aspects of the check engine light is its ambiguity. Unlike other dashboard warning lights that specify a particular problem, the check engine light is more like a general alert signal. It doesn't provide details about the exact nature of the issue, leaving drivers wondering whether it's a minor glitch or a major mechanical failure. In order to determine the actual reason why the check engine light is aluminate you will need some specialized tools.

The diagnostic process almost always involves the use of specialized OBD2 scan tools. Some people may assume that it is a good investment to buy one especially since you can get one on online stores like Amazon and eBay for under $50 however, the problem is those tools may not help you determine the cause of your specific check engine cause. There is a reason why mechanics often opt for more advanced scan tools from reputable brands like Autel and SnapOn because they offer more precise readings and support a wider range of vehicle years, makes and models.

Diagnostic Process

If you choose to invest in the higher-end scan tools, there's still the challenge of understanding how to use them effectively and interpret the results. For those without experience and access to service manuals, using these tools and interpreting the error codes can be challenging, as it may feel like working blind without the necessary expertise.

In many late model vehicles, the failure of one system will automatically disable another system causing different error codes that arise as a response to the main fault. For example, on most late model Subarus if there is any fault that creates a check engine worthy code it will also trigger the ABS and traction control system codes. So, for the person that is not aware of this they may be stuck trying to fix issues with the brake system rather concentrating on the main code causing all the consequent codes. The issue if further compounded by the vast amount of engine codes on various vehicle years makes and models. It is not uncommon to see over 10 consequent codes on German vehicles which are resolved as soon as the main fault is fixed. Knowing which code to chase after is not something you will be able to learn overnight.

While the check engine light can illuminate for a variety of reasons, some common causes include:

• Loose Gas Cap: Surprisingly, a loose or improperly tightened gas cap is one of the most frequent culprits behind a check engine light. This simple oversight can trigger the emission control system to detect a leak and illuminate the warning light.

• Faulty Oxygen Sensor: The oxygen sensor measures the amount of oxygen in the exhaust gases and helps regulate fuel mixture for optimal engine performance. A malfunctioning oxygen sensor can lead to reduced fuel efficiency and increased emissions.

• Catalytic Converter Issues: A clogged or damaged catalytic converter can trigger the check engine light, indicating a potential problem with emissions control. In cases where the issue is not addressed exhaust pressure build up can occur that can lead to more serious problems. In addition, catalytic converter related engine codes tend to be the most common reasons vehicles fail state mandated emissions test.

• Faulty Mass Airflow Sensor: Similar to the O2 sensor the mass airflow sensor monitors the amount of air entering the engine and plays a crucial role in the fuel to air mixture and combustion. A faulty sensor can cause engine performance issues and trigger the check engine light.

• Electrical Issues: Most common electrical issues usually have to do with faulty ignition coils, worn-out spark plugs and can disrupt the combustion process, leading to engine misfires and reduced performance. These issues often trigger the check engine light.

To accurately gauge the severity of the problem, it's crucial to conduct the diagnostic process properly, as the seriousness of the issue signaled by the check engine light can vary significantly. In some cases, it may be a minor, easily resolvable issue like a loose gas cap. Alternatively, it might signify a more critical issue demanding immediate attention, like a faulty catalytic converter or other severe malfunctions.

Repair Process

If you are able to troubleshoot the problem and properly diagnose the cause of the check engine light now you will need to find a repair manual for that specific fault. The mechanics go to for repair and service manuals is alldata.com. This service offers vehicle technicians quick and easy access to a vast amount of data however, it is not free. Since this service is meant for automotive technicians, it is only offered as a paid subscription targeting car repair shop businesses. However, there are some free alternatives like charm.li, you may even be able to find a free video repair tutorial on youtube.com. Granted the coverage of these free resources may not be as good and you may struggle finding the correct repair manuals for your year make and model vehicle it is still possible to find many of them online for free.

Once you have obtained the repair manual you must then be able to follow the technical instructions. The repair may also include the use of some specialized tools which you will need to acquire. If you only need these tools for a one-time repair, consider renting them from certain establishments. Some auto parts stores like AutoZone provide tool rental programs, offering the equipment at a fraction of the purchase cost. In some instances, they may even provide rentals for free if you make a purchase from their store.

Now that you've gathered all the necessary tools, you'll also need a moderate understanding of disassembling and assembling mechanical components, disconnecting wiring connectors, and familiarity with mechanical and electronic systems. Keep in mind that some repairs may be more intricate than others, so it's essential to be aware of your limitations. As mentioned earlier, we highly advise against attempting the process yourself if you lack any experience.

No one enjoys seeing the check engine light illuminate in their vehicles gauge cluster, it's essential not to panic. In many cases, it may indicate a relatively minor issue that can be addressed by a qualified mechanic. However, it's crucial not to ignore the warning light, as doing so could lead to more severe problems down the road.

If you're purchasing a vehicle and find solace in the absence of error messages on the gauge cluster, don't assume it's free from any preexisting issues. Unfortunately, some sellers employ a dishonest practice of clearing error codes just before selling the car. Most error codes won't immediately reappear until the car's computer has analyzed all systems during various driving conditions. It's not uncommon for pre-owned car buyers to encounter a check engine light after owning the car for a while or driving it for up to 150 miles, as some codes may remain dormant. The only reliable way to detect dormant codes is by having a professional technician scan the car. They can identify any potential codes or recent erasures from the car's error code history, ensuring a more transparent transaction. It is also strongly suggested that you do a vehicle vin lookup prior to agreeing to purchase the car. You can run a full vehicle vin check with one simple search on vincheckup.com and get related details about the vehicles condition, past accidents, floods, fires, and much more…