Check Engine Light On? Here's What It Might Mean

Frank’s Country Auto – 6377 Partners Ave, Marion, IA 52302 | Call 319-200-4384

There’s nothing quite like that sinking feeling you get when your check engine light suddenly turns on. It always seems to happen at the worst time—on the way to work, during a family road trip, or right before an important appointment. Your vehicle might feel fine, or it might start acting up—but either way, the warning is clear: something needs attention.

At Frank’s Country Auto in Marion, Iowa, we’ve helped countless drivers get to the bottom of that mysterious dashboard light. Whether it’s a minor fix or a more serious issue, our goal is to give you clear answers, honest advice, and professional repairs that get you safely back on the road.

So if your check engine light is on, here’s a breakdown of what it might mean—and what you should do about it.

What Is the Check Engine Light?

The check engine light, also known as the malfunction indicator lamp (MIL), is part of your vehicle’s onboard diagnostics system (OBD-II). It alerts you when your vehicle's engine or emissions system is not working properly.

Depending on your make and model, it might appear as a solid or blinking light, often shaped like an engine icon or simply labeled “Check Engine.” This light doesn’t mean immediate disaster—but it should never be ignored.

Should I Panic When the Check Engine Light Comes On?

Not necessarily—but you should act quickly. Some issues are minor and inexpensive to fix. Others, if ignored, can lead to serious engine damage or safety hazards.

Here's how to respond:

Solid Light: Generally indicates a non-urgent issue. Still important, but you likely have time to schedule service.

Flashing Light: This is more serious. A flashing check engine light usually points to a severe misfire that can damage your catalytic converter or engine. Stop driving and call Frank’s Country Auto at 319-200-4384.

Top Reasons Your Check Engine Light Might Be On

Let’s explore some of the most common culprits behind a triggered check engine light—and how we diagnose and fix them at Frank’s Country Auto.

1. Loose or Damaged Gas Cap

Believe it or not, one of the most common—and easiest to fix—reasons for a check engine light is a loose or cracked gas cap. Your fuel system is pressurized, and the gas cap helps maintain that pressure.

What it means:

A loose gas cap can cause fuel vapors to leak and trigger an emissions code.

What to do:

Tighten the gas cap until it clicks. If the light doesn’t turn off after a few trips, stop by our shop for a free code scan.

2. Faulty Oxygen Sensor (O2 Sensor)

Your car’s oxygen sensors monitor how much unburned oxygen is in your exhaust system. A failing sensor can throw off your fuel-to-air ratio, reduce fuel economy, and increase emissions.

What it means:

The engine may run too rich (too much fuel) or too lean (too much air), harming performance.

Symptoms:

Poor fuel mileage

Rough idling

Failed emissions test

Fix:

We’ll scan the code, verify the faulty sensor, and replace it with a high-quality part.

3. Bad Catalytic Converter

The catalytic converter reduces harmful emissions by converting toxic gases into less harmful substances. A failing converter can cause your car to lose power, increase emissions, and even damage your engine.

What it means:

Your emissions system isn’t working properly, and the problem may worsen with time.

Symptoms:

Sulfur (“rotten egg”) smell

Poor acceleration

Decreased fuel economy

Fix:

This is a costly but crucial component. We’ll test the converter’s efficiency and determine if replacement is necessary.

4. Malfunctioning Mass Airflow Sensor (MAF)

The MAF sensor measures how much air enters the engine so the computer can inject the correct amount of fuel.

What it means:

Too much or too little fuel is reaching the engine, leading to poor performance.

Symptoms:

Hesitation when accelerating

Engine stalling

Check engine light + P0101 or P0102 code

Fix:

We’ll clean or replace the sensor and reset your light.

5. Worn or Faulty Spark Plugs/Ignition Coils

Spark plugs ignite the fuel-air mixture in your engine. When they fail—or when ignition coils supplying electricity to the plugs go bad—you can experience misfires.

What it means:

Your engine is misfiring, potentially damaging the catalytic converter or engine block.

Symptoms:

Rough running

Poor acceleration

Engine shaking

Fix:

Replacing spark plugs or coils is typically straightforward and affordable.

6. Faulty EGR Valve

The exhaust gas recirculation (EGR) valve recycles exhaust gases back into the engine to reduce emissions. A stuck or clogged valve can cause performance issues.

Symptoms:

Engine knocking

Poor fuel economy

Check engine light + EGR-related codes

Fix:

We inspect the valve and clean or replace it depending on its condition.

7. Vacuum Leak

Your engine relies on a network of vacuum hoses to control airflow. A leak—due to cracked or disconnected hoses—can trigger lean conditions that trip the light.

Symptoms:

Rough idle

High or fluctuating RPMs

Hissing sound from engine bay

Fix:

We'll use smoke testing or sensor data to locate the leak and restore proper function.

8. Transmission Issues

In some vehicles, the check engine light is also triggered by transmission faults—such as slipping, rough shifting, or fluid problems.

Symptoms:

Delayed or hard gear shifts

Slipping in or out of gear

Warning lights for “transmission” or “service vehicle soon”

Fix:

We scan the vehicle using advanced diagnostic tools to identify the exact problem before recommending repairs.

9. Aftermarket Parts or Sensors

If you’ve recently installed a new battery, alternator, remote starter, or aftermarket stereo, improper installation or incompatible parts can interfere with your vehicle’s electronic systems.

Symptoms:

Intermittent check engine light

Electrical glitches

Poor drivability

Fix:

We’ll check your vehicle’s modules for compatibility and wiring issues.

How We Diagnose a Check Engine Light at Frank’s Country Auto

When you visit us at 6377 Partners Ave in Marion, we use high-end diagnostic equipment to:

Scan the Codes:

Read your vehicle’s OBD-II trouble codes using a professional scan tool.

Interpret the Codes:

Codes like P0420, P0171, or P0300 don’t always mean “replace a part.” Our technicians dig deeper to determine root causes.

Perform Visual & Functional Tests:

We inspect sensors, wiring, connectors, and components to verify failures.

Explain in Simple Terms:

You’ll get a clear, honest explanation of what’s wrong and what your options are.

Repair & Reset:

Once approved, we perform the necessary repairs and clear the code, ensuring the light stays off.

What Happens If I Ignore the Check Engine Light?

Ignoring the light can lead to:

More expensive repairs later

Poor fuel efficiency

Performance issues

Engine damage

Failed emissions test (which matters in counties with emissions regulations)

Voided warranty, in some cases

Even if your car seems to run fine, it’s better to have it checked now than to pay more later.

Why Choose Frank’s Country Auto in Marion, Iowa?

At Frank’s Country Auto, we know how frustrating vehicle issues can be—especially when you don’t know who to trust. That’s why we focus on clear communication, fair pricing, and fast turnaround.

✅ Honest, upfront diagnostics

✅ High-quality parts and repairs

✅ Experienced, ASE-certified technicians

✅ Locally owned and operated

✅ Friendly service that puts your needs first

We’ve built our reputation in Marion, IA, by helping families and businesses stay safe and on the road.

Schedule a Diagnostic Today

If your check engine light is on, don’t stress—just call us. We’ll take the mystery out of that glowing dashboard and get your car fixed right the first time.

📍 Visit us at 6377 Partners Ave, Marion, IA 52302

📞 Call us at 319-200-4384

🕒 Convenient scheduling Monday–Friday

At Frank’s, we’ll treat you like family and your vehicle like it’s our own.

Frank’s Country Auto – Your Local Partner for Honest Auto Service in Marion.

When the light comes on, we’re the ones to call.