What to Do When Your Check Engine Light Comes On

If your dashboard is displaying a Check Engine light, identifying the cause can prevent damage to your engine and keep your vehicle performing its best. At O’Reilly Auto Parts, our Professional Parts People are here to help you determine what your Check Engine Light means and get you back on the road safely.

Whether your Check Engine light is solid or flashing, understanding the meaning of your diagnostic trouble codes (DTCs) is the first step. Keep reading to learn how to address an active light, identify the common components involved, and how to utilize free O’Reilly VeriScan Check Engine light testing to find the solution you need.

A Check Engine light, or malfunction indicator lamp (MIL), is part of your vehicle's On-Board Diagnostics II (OBD-II) system. Since 1996, this standardized system has monitored the performance of the engine, transmission, and exhaust system.

The light activates when the engine control module (ECM) detects sensor data that falls outside of the factory-programmed range. This could appear as an engine symbol or text like “Check Engine” or “Service Engine Soon.” When this happens, the computer logs a specific code that indicates which system or component is struggling to function properly, or what symptom or measurement error has been observed.

Because the Check Engine light is a general alert, it doesn't pinpoint the exact part that needs to be replaced just by looking at your dashboard. Think of the light as a symptom rather than a final diagnosis. To find the right solution, our parts professionals use FREE O’Reilly VeriScan Check Engine light testing to retrieve the diagnostic trouble codes stored in your vehicle's computer.

While there are thousands of possible codes, our Professional Parts People find that these common components are most frequently responsible for triggering the light:

If your Check Engine light is on, how long you can continue to drive depends entirely on the light’s behavior and your vehicle’s performance. If you notice a sudden loss of power, a rough idle, or a stuttering sensation, you should seek a diagnosis immediately to prevent internal engine damage.

Depending on the severity of the symptoms, it may be best to stop driving immediately to prevent catastrophic engine failure or permanent damage.

Solid Check Engine Light

A solid Check engine light indicates that a fault has been detected that often affects emissions or fuel economy, but it isn’t an immediate emergency. You can typically continue driving, but you should visit your Local O’Reilly Auto Parts for a free scan as soon as possible to avoid long-term damage to components like your catalytic converter.

Flashing Check Engine Light

A flashing Check Engine light is a critical warning that indicates a severe engine misfire or other issue that can lead to immediate engine damage. In this state, unburned fuel can also enter the exhaust system and destroy your catalytic converter in minutes. If the light flashes, pull over safely and turn off the engine immediately to prevent catastrophic engine failure.

To turn off a Check Engine light, you need to address the specific mechanical or electrical fault that triggered the alert. While it may be tempting to clear the codes by disconnecting the battery, this is typically a temporary measure.

Your vehicle's computer begins a "re-learn" process as soon as the engine starts; if the underlying problem hasn't been fixed, the computer will detect the fault again and turn the light on within a few miles.

Once the repair has been completed, a technician can use an OBD-II tool to clear the code and verify that the system is back to normal. Even without clearing the code, Check Engine lights will often turn off on their own once the repair is completed and the fault is no longer being detected.

While the Check Engine light warns you of a current problem, staying on top of your vehicle’s maintenance schedule can help ensure your sensors and ignition components last their full service life.

• Replace Spark Plugs Regularly: Worn spark plugs require more voltage to fire, which puts extra strain on your ignition coils. Replacing them at recommended intervals helps prevent the engine misfires that lead to a flashing Check Engine light.
• Inspect Fuel Filters: Clean filters ensure your engine receives the proper flow of air and fuel. This allows the computer to maintain a perfect air-fuel ratio, preventing lean or rich condition codes that trigger the light.
• Monitor Your Braking System: If your brake pedal pulses or you hear a high-pitched squeal, it is time for a brake inspection. Addressing thin pads early prevents "metal-on-metal" contact that can lead to damaged rotors. Though brake issues aren’t typically recognized by the engine control module, they could trigger other warnings like ABS lights. O’Reilly Veriscan can also read ABS codes to assist you with diagnosing and repairing your brake system issues, where applicable.
• Keep Fluids Topped Off: Modern engines use oil pressure to adjust internal timing components. If your oil level is too low, it can trigger timing-related Check Engine light codes before any mechanical damage occurs. Coolant levels can also affect engine performance and efficiency. Ensuring the right type and amount of coolant is used and that regular coolant flushes are completed can help extend engine life and prevent overheating.

Don't let a dashboard warning cause unnecessary stress. Whether you need O’Reilly VeriScan Check Engine light testing or the high-quality parts to complete a DIY maintenance project, the Professional Parts People at your local O'Reilly Auto Parts are ready to help you find the right solution and get the job done right.

What is the most common reason for a Check Engine light?

The most frequent cause is often a loose or damaged gas cap that isn't sealing properly. Other common issues include failing oxygen sensors, worn spark plugs, or a clogged catalytic converter. Since the light is a general warning, free O’Reilly VeriScan Check Engine light testing is the best way to identify the specific problem.

What does a flashing Check Engine light mean?

A flashing Check Engine light indicates a severe engine misfire or another issue that could lead to catastrophic engine failure. This is an emergency because unburned fuel can enter your exhaust and destroy your catalytic converter in minutes, or the engine may suffer internal damage due to rough or erratic operation. If the light flashes, pull over safely and turn off the engine immediately to prevent extensive and costly damage to your vehicle.

Can low oil cause the Check Engine light to turn on?

Yes. Modern engines use oil pressure to control internal parts that adjust engine timing. If your oil level is too low, parts that rely on oil pressure can’t function correctly. This triggers the Check Engine light to warn you of potential timing issues or engine damage before the problem becomes serious.

How can I tell if a Check Engine light is serious?

A solid Check Engine light with no change in driving feel indicates you should get a diagnostic scan soon. A solid light accompanied by shaking, stalling, or a drop in fuel efficiency requires immediate attention. A flashing Check Engine light is an emergency. Pull over safely and stop driving immediately to avoid potential engine damage, and stop by your local store for an O’Reilly Veriscan as soon as possible.

Does O’Reilly Auto Parts scan Check Engine lights for free?

Yes. If your Check Engine light is on, visit your local O’Reilly Auto Parts for free O’Reilly VeriScan Check Engine light testing. We can scan most vehicles from 1996 to the present by plugging our code reader into your OBD-II system port. Our parts professionals will provide a report of your trouble codes, repair options, and suggested parts.