Why Is My Check Engine Light On?

It’s rarely a pleasant experience to see your check engine light illuminate on the dashboard. Much of the discomfort of seeing this light is that drivers often don’t know the cause. There are many causes of the check engine light turning on, and they range from minor to major. This article highlights some of the most common reasons for the check engine light illuminating your dashboard. You’ll also get some tips on what to do if the check engine light turns on.

Common Causes of Check Engine Light Switching On

“Gas Station Refilling” used with permission via Pixabay by JirkaF

Damaged Spark Plugs

Worn or damaged spark plugs can cause misfiring issues with a car’s engine. The spark plug is the source of electricity that ignites the mixture of air and fuel needed for your engine to produce power. Spark plugs are not as difficult to change as you might think and they are also quite cheap, so this cause of an engine light switching on isn’t as disastrous as it might sound.

Loose Fuel Cap

One of the most common causes of the check engine light switching on is a loose fuel cap. The cap prevents gasoline fumes from emitting out of the fuel tank while also ensuring the correct pressure for fuel delivery. If a loose fuel cap is the cause of your check engine light turning on, it’ll most commonly happen after a visit to a gas station.

Sometimes you might not have fastened the cap back on properly. Other times, you may have even mistakenly left the cap on the roof. Wear and tear can also cause the cap not to fit correctly. Regardless of the reason that the fuel cap is loose, it’s typically an easy and cheap fix.

Faulty Catalytic Converter

A catalytic converter converts harmful substances created during engine combustion into less harmful substances. For example, harmful gases like carbon monoxide and nitric oxide are turned into carbon dioxide and water vapor.

Sometimes the catalytic converter becomes clogged and eventually fails, which results in the check engine light illuminating. Some useful ways to prevent catalytic converter failure include driving longer distances and ensuring you take your vehicle for regular maintenance checks.

Oxygen Sensor Failing

Oxygen sensors are critical components of most modern gasoline-powered vehicles. Oxygen sensors monitor the oxygen levels inside the exhaust to help the vehicle determine the correct fuel-to-air ratio. A failing oxygen sensor typically leads to sub-optimal fuel-to-air ratios, which results in increased emissions.

Another symptom of a failing oxygen sensor is reduced performance. If you haven’t noticed increased emissions or performance issues like stalling, an obvious sign of a failing oxygen sensor is the check engine light turning on.

Bad Spark Plug Wires

In order for the spark plug to work correctly in a car, an electrical current has to travel from the vehicle’s ignition coil to the plug. The medium by which electricity transfers to a spark plug is the spark plug wire. Faulty spark plug wires cause noticeable performance issues, including rough engine idle and reduced fuel economy. A faulty spark plug wire also triggers the check engine light to turn on. Thankfully, you can get your spark plug wires replaced without having to break the bank.

Aftermarket Car Alarm

A surprisingly common cause of the check engine light turning on is a malfunctioning or poorly installed aftermarket car alarm. Many people choose to install their own aftermarket alarm because these alarms typically provide advanced security features not included with the standard manufacturer-installed alarms. An improperly installed aftermarket alarm often triggers the check engine light to turn on, which will warrant a visit to a mechanic to get it installed properly.

What To Do About the Check Engine Light

The most important thing to keep in mind is that you shouldn’t ignore the light. Whether the cause is minor or major is something that you need to find out. Some vehicles make it easier to distinguish between minor and major causes of check engine lights switching on by using different color shades depending on issue severity. For example, major causes needing immediate attention will cause the light to flash red.

If you’re driving a vehicle that doesn’t distinguish between minor and major reasons for switching the engine light on, the best thing to do is pull over as soon as it’s safe to do so. Start with the easiest fix, which is to tighten the fuel cap. If fastening the fuel cap works, the problem is solved.

If tightening the fuel cap doesn’t fix the check engine light issue, you then have to decide whether it’s appropriate to take your vehicle to your local dealership. Unless you have a code reader that can decipher what’s causing the engine light to switch on, it’s best to visit a competent mechanic who can find out this information for you. The problem might be as simple as replacing the spark plug wire, which is an inexpensive fix.

It’s worth noting that aside from color-coded warnings, the check engine light often behaves in different ways. For example, the light might only flicker inconsistently or it might stay constantly on. Performance problems coupled with an engine line that illuminates constantly indicates a severe issue that requires immediate attention. The light sometimes flashes steadily in a rhythmic pulsing pattern, and this often indicates a serious issue with the catalytic converter.

If you really want to avoid a trip to the mechanic, you’ll need a Bluetooth OBDII scanner. You’ll have to pair your scanner with a compatible app, find the OBDII port in your car, and read the code that comes up. Sometimes the app shows you what the code means, however, you might need to look in a repair manual or on the Internet for an explanation. It’s worth also remembering that these code scanners aren’t as advanced as the professional-grade ones typically used by mechanics to diagnose check engine light causes.

Hopefully, this article has cleared up some of the main reasons for a check engine light turning on. As you can tell, the best person to address most issues beyond a loose fuel cap is a qualified mechanic. The Service Department at Volkswagen of Marion can help diagnose your engine problem. Contact us today to get your car serviced.