Why Is My Check Engine Light On? Common Reasons and What to Do Next

Seeing that little orange or yellow light pop up on your dashboard can make any driver uneasy. If you’re searching why is my check engine light on, the good news is: not every warning means a major repair — but every warning does mean don’t ignore it. In this post, we’ll cover the most common causes, what they mean, and how Marble Falls Auto Center can help get to the bottom of it fast.

Loose or Faulty Gas Cap

Believe it or not, a loose gas cap is one of the most frequent and easily fixable reasons for a check engine light. If the cap isn’t sealed tight, your car's evaporative emissions system detects a leak.

What to look for:

• Gas cap appears cracked, missing, or loose

• The light comes on right after refueling

What to do: Tighten the cap until it clicks. If the light doesn’t turn off after a few trips, visit Marble Falls Auto Center to inspect the emissions system.

Faulty Oxygen Sensor

Oxygen (O2) sensors monitor the level of oxygen in your exhaust and help regulate your fuel-to-air mixture. When one fails, fuel efficiency drops and emissions rise.

Common symptoms:

• Rough idling

• Decreased MPG

• Check engine light plus sluggish performance

We can scan your OBD-II system and replace a failing sensor before it affects other parts, like your catalytic converter.

Failing Catalytic Converter

The catalytic converter reduces harmful emissions and helps your engine run clean. If it's failing, it could trigger a check engine light and reduce performance.

Signs include:

• Rotten egg smell from exhaust

• Poor acceleration

• Reduced fuel economy

This is a critical component — let Marble Falls Auto Center diagnose and replace it before it leads to bigger problems.

Why Is My Check Engine Light On? Common Reasons and What to Do Next

Bad Spark Plugs or Ignition Coils

Worn spark plugs or coils can misfire, causing unburnt fuel to enter the exhaust. This not only trips the check engine light but can damage your engine if ignored.

Look for:

• Engine misfiring or stuttering

• Poor gas mileage

• Difficulty starting your car

We’ll check your ignition system and replace spark plugs or coils to restore smooth performance.

Mass Airflow Sensor Issues

The mass airflow (MAF) sensor helps your engine manage how much air is entering the system. When it fails, it can cause imbalance and trigger the light.

Symptoms:

• Jerky acceleration

• Hard starts

• Poor fuel economy

We’ll inspect and clean or replace your MAF sensor as needed.

Final Thoughts

If you’ve been wondering why is my check engine light on, the safest move is to have your vehicle scanned by a certified technician. What starts as a small sensor issue can lead to more serious — and expensive — damage if left unresolved.

At Marble Falls Auto Center, we offer full diagnostics with the latest tools to pinpoint the problem fast. Whether it’s a gas cap or a major repair, we’ll give you a clear answer — and a reliable solution.

Don’t guess. Don’t wait. Come see us today and let’s turn that light off for good.