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What Does a Check Engine Light Mean? How to Troubleshoot

February 5, 2024

You’re cruising down the road, and all seems well as your car hums along smoothly. Suddenly, you see something come up on the dashboard: an orange light (or icon) — this nasty symbol appearing on your dash can be concerning when it randomly shows up, but what does the check engine light actually mean when it pops up? 

Unfortunately, there isn’t just one answer to this. When the engine light comes on, it can signal several potential issues. Let’s look at the possible reasons behind the light and dive into the recommended actions you can take to address them.

What Does A Check Engine Light Look Like?

6 different versions of what a check engine light can look like in a vehicle
Image Credit: Getty / Ihor Kashurin

Each vehicle can have a different check engine light displayed but they all have the same meaning. The check engine light differs by vehicle brand, model, year, etc. Here are a few examples:

  • Engine icon
  • Engine icon with an electrical arrow through it
  • Engine icon with “CHECK” or “CHECK ENGINE” text
  • “CHECK ENGINE” text

Why Is My Check Engine Light On?

So, your check engine light came on, now what? The next step is troubleshooting the check engine light. Common check engine light reasons include: 

  1. A loose gas cap
  2. A bad tank of gas
  3. Malfunctioning oxygen sensor
  4. Faulty spark plugs, spark plug wires, and ignition coils
  5. Catalytic converter issues
  6. An internal engine issue

Common Issues & How To Troubleshoot Each

Trying to fix a check engine light can be tricky if you don’t know what to look for. There are some easy fixes that can be done but some problems might not be visible to you without an OBD code reader. This reader (or scanner) can help you run diagnostics on the vehicle so you’re not testing everything out to see what is or isn’t working.

You can either take it to the shop to get it read (for a fee) or you can get an OBD code reader yourself, run it on the vehicle, and dissect what code(s) it’s telling you.

With or without a code reader, here’s what to do when the check engine light comes on:

  • A Loose Gas Cap: One of the most common triggers for the check engine light is a loose gas cap. The cap serves to seal the fuel system and prevent evaporation, and if it’s not securely tightened, it can lead to a drop in pressure, causing the warning light to illuminate. This is a super easy fix, simply tightening the gas cap may resolve the issue. Try listening for that “click” when you tighten the cap to know it’s securely fastened.
  • A Bad Tank of Gas: Poor-quality or contaminated fuel can also prompt the check engine light. Impurities in the gas can affect engine performance and trigger sensor alerts. In such cases, it’s advisable to run the tank nearly empty before refueling with a reputable brand of gasoline. Choose your gas station wisely. You can also put fuel treatment in to help try to clean up the impurities in the gas.
  • Malfunctioning Oxygen Sensor: The oxygen sensor monitors the level of oxygen in the exhaust gasses. A malfunctioning sensor can disrupt the engine’s fuel efficiency and emissions control. Replacing a faulty oxygen sensor can often resolve this issue and improve overall engine performance. There might be other engine-related issues that could cause the oxygen sensor to read incorrectly. If this is the case, you may have to take it to a repair shop to fix the root cause.
  • Faulty Spark Plugs, Spark Plug Wires, and Ignition Coils: Problems with the ignition components, such as worn-out spark plugs, damaged spark plug wires, or malfunctioning ignition coils, can lead to misfires and trigger the check engine light. Regular maintenance and check-ins can prevent the electrical components of your vehicle from going bad. Timely replacement of these components can solve issues with the electrical parts so you don’t end up having more problems.
  • Catalytic Converter Issues: A failing catalytic converter can result in increased emissions and trigger the check engine light. Issues may include overheating, clogging, or physical damage. Diagnosing and addressing catalytic converter problems promptly is crucial to maintaining proper emission control and engine efficiency.
  • An Internal Engine Issue: The check engine light may indicate more serious internal engine problems, such as issues with the valves, pistons, or other crucial components. Diagnosing and addressing internal engine issues often requires professional expertise and may involve a thorough inspection using diagnostic tools to pinpoint the exact problem. Early detection and resolution are key to preventing further damage.

Check Engine Light When It’s Static Vs. Flashing

The check engine light’s meaning depends on whether it’s flashing or remains static (solid).

If your ride’s rocking an orange check engine light on the dashboard, no need to go full panic mode. While it signals an issue, chances are it’s not a catastrophic engine failure. If that were the case, your vehicle would likely be giving you a heads-up about how it’s behaving — or not behaving. 

Less serious check engine issues include:

  • Loose Gas Cap: A loose gas cap can trigger the light. Ensure it’s tightened securely to maintain proper pressure in the fuel system.
  • Oxygen Sensor Malfunction: While not an emergency, a malfunctioning oxygen sensor can affect fuel efficiency and emissions. Replacing it on time is advisable.
  • Faulty EGR Valve: A malfunctioning Exhaust Gas Recirculation (EGR) valve may trigger the light. Though not urgent, addressing it can enhance fuel efficiency and reduce emissions and power.
  • Minor Vacuum Leak: Small vacuum leaks can trigger the light. Identifying and fixing these leaks can improve engine performance over time.

Keep cruising (maybe with a tad more caution) and schedule your car for some diagnostics as soon as possible just in case it’s a bigger issue.

If that light blinks a solid red or orange instead of yellow, that’s a different story. Your engine light is signaling issues that could lead to immediate damage. In this case, it’s best to pull over and address the problem.

Critical issues include:

  • Misfiring Engine: A misfiring engine can lead to permanent damage if not addressed promptly. It’s often linked to ignition system problems, such as faulty spark plugs or ignition coils.
  • Catalytic Converter Failure: Issues with the catalytic converter can escalate emissions problems and harm overall engine performance. Timely action is essential to prevent costly repairs.
  • Overheating Engine: An overheating engine can result from various issues, including a malfunctioning cooling system or a faulty thermostat. Immediate intervention is crucial to prevent engine damage.
  • Low Oil Pressure: Low oil pressure can lead to insufficient lubrication, causing extensive engine damage. This could be a result of oil leaks, a failing oil pump, or low oil levels.

What Happens If You Ignore The Check Engine Light?

Brushing off that lit-up warning sign and delaying a visit to the mechanic could land you in a fix with pricier and more time-consuming challenges down the road.

The issue that triggered your check engine light initially might escalate or mess with other parts of your car’s engine or transmission. Ignoring the glitch could lead to sustained damage not covered by your car insurance.

Plus, acing your next car inspection is a no-go until the check engine light takes a hiatus and the issue is sorted out. The smart move? Tackling the problem pronto. If the worry of unexpected engine repairs nags at you, consider checking out mechanical breakdown insurance.

Additionally, learning how to make the necessary repairs yourself and how to troubleshoot more extensive issues will be your best bet in keeping your ride in the best shape possible.

Troubleshoot Any Vehicle Issue Like a Pro

There is so much more you need to know about vehicle maintenance other than a check engine light. 

Ranked among the premier automotive trade schools nationwide, WyoTech is dedicated to equipping students for a thriving career in the automotive, diesel, auto body, and welding industries. 

Our classes are led by seasoned experts, offering you the opportunity to collaborate with some of the most brilliant minds in these fields, fostering a dynamic learning environment among your fellow aspiring mechanics.

Reach out to us today to explore how you can kickstart your career in working with vehicles.