Can you drive with a malfunction indicator light on?

In most cases, you can drive for a short period when the check engine light—officially the malfunction indicator light (MIL)—activates, but you should treat it as a warning and avoid long trips. If the light is blinking, it’s a much more urgent signal that you should stop as soon as safely possible.

The MIL can come on for many reasons, from a loose gas cap to a misfiring engine or a faulty emissions sensor. The specific fault is stored as a diagnostic trouble code (DTC) that a mechanic reads with an OBD-II scan tool to determine next steps. The difference between a steady glow and a blinking light helps judge urgency and risk to the catalytic converter and other components.

What the light means

The malfunction indicator light is a dashboard warning that the vehicle’s onboard computer detected a fault that could affect engine performance or emissions. While some causes are minor, others can threaten engine reliability or fuel efficiency if not addressed. A professional diagnosis uses stored DTCs to identify the faulty subsystem.

Common causes range from simple, verifiable issues to components that may require service. Knowing the likely categories helps drivers decide how to respond and when to seek help.

Before reviewing typical causes, note that codes will guide the next steps. Common categories include sensor faults, emissions system problems, ignition issues, and fuel delivery concerns.



• Loose or damaged gas cap


• Faulty oxygen sensor or other emissions sensors


• Ignition system problems (spark plugs, coils, wires)


• Mass airflow (MAF) or airflow-related sensor faults


• Catalytic converter or exhaust system issues


• Fuel injector or fuel delivery problems


• Engine misfire or running conditions causing poor performance

Even when the light appears minor, the underlying issue can worsen over time or cause higher emissions. A timely diagnosis helps prevent costly damage and ensures the vehicle remains safe and compliant with local standards.

Blinking vs solid: Immediate steps

Before taking action, distinguish between a blinking MIL and a solid MIL. The blinking light signals a misfire or serious fault that can quickly harm the catalytic converter and should prompt immediate action.

Use these guidelines to decide how to proceed when you see the MIL:



• Blinking MIL: Stop driving as soon and safely as possible. A misfire or severe engine fault can overheat the catalytic converter. If you can safely reach a repair facility, do so; otherwise, call roadside assistance.


• Solid MIL: You can usually drive temporarily, but avoid stressing the engine. If you notice rough running, loss of power, severe fuel consumption changes, or unusual noises, limit driving and seek service promptly.

Regardless of whether the light is blinking or solid, plan to get the vehicle checked soon. Driving with an MIL on can worsen the fault, damage emissions systems, or cause fuel economy to deteriorate.

What to do next: practical steps

To address a MIL responsibly, follow a structured approach to identify the fault and prevent further damage. The steps below are practical actions most drivers can take, especially before a formal diagnostic from a shop.

• Check the gas cap: Ensure it’s fully tightened. A loose cap is a frequent cause of MIL illumination and can sometimes turn off the light after a few drive cycles.


• Note any symptoms: Record any rough idling, misfiring, stalling, reduced power, or strange sounds and smells to share with a technician.


• Read the code: Use an OBD-II scanner (or have a parts store read the code for free) to identify the diagnostic trouble code (DTC).


• Research the DTC: Look up the code to understand likely causes and urgency; some codes point to minor fixes, others to critical issues.


• Plan a service visit: Schedule a diagnostic with a qualified mechanic or dealership to pinpoint the fault and determine necessary repairs.

If you’re in an area with emissions testing, an active MIL can affect inspection eligibility. A confirmed fault may require repair and retesting before passing.

Summary

A malfunction indicator light on your dashboard generally signals a fault in the engine or emissions system. A blinking MIL is an urgent warning that requires immediate attention and usually signals a misfire or severe fault. A solid MIL may allow short driving to a repair shop, but it should not be ignored, as it can indicate issues ranging from a loose gas cap to sensor failures or catalytic converter problems. Obtain a diagnostic code, assess symptoms, and schedule service promptly to protect engine health, fuel efficiency, and regulatory compliance.

Is it safe to drive with an engine malfunction light?

You can likely drive with a solid check engine light, but a flashing light means you should pull over immediately and seek professional help. If the light is solid, drive cautiously to a mechanic and avoid heavy driving until the issue is diagnosed, as it could be a minor problem like a loose gas cap or a more serious one like a faulty catalytic converter. 
If the check engine light is solid:

• Drive cautiously: It's generally safe to continue driving, but reduce your speed and avoid hard acceleration, heavy loads, or towing. 
• Check the gas cap: Pull over when it's safe and ensure your gas cap is tight. Tighten it and continue driving; the light may turn off after a few trips. 
• Look for other symptoms: Pay attention to any changes in your car's performance, such as strange noises, loss of power, or smoke. If you notice any, pull over as soon as possible. 
• Schedule a diagnostic check: Make an appointment to have the car scanned by a mechanic as soon as you can. 

If the check engine light is flashing:

• Pull over immediately: A flashing light indicates a serious problem, such as a misfire, that could cause significant damage to your engine or catalytic converter. 
• Turn off the car: Once you've pulled over to a safe location, turn off the engine. 
• Do not drive: Do not attempt to drive further. Have the vehicle towed to a repair shop for an inspection. 

How long can you drive with a malfunction indicator light?

It is safe to drive your car for 50 to 100 miles. If there is an issue with the sensor, turning the check light off takes some time. But if it is a serious issue behind the checked light, it will probably start blinking. Blinking the check engine light indicates immediate attention.

What do you do if your malfunction indicator light comes on?

When the malfunction indicator light comes on, check for a loose gas cap and then have the vehicle's codes read with an OBD-II scanner to identify the specific problem. If the light is flashing, or if you notice other serious symptoms like a loss of power or strange noises, pull over safely, turn off the engine, and consider having the vehicle towed.
 
This video explains what to do when the check engine light comes on: 57sThe_Car_MomYouTube · May 12, 2023
Immediate actions

• Check for a loose gas cap: The most common cause is a loose or faulty gas cap. Tighten it completely and see if the light turns off after a short drive. 
• Look for other signs: Pay attention to how the car is performing. Are there other warning lights on? Is the engine running rough? Is there a loss of power or strange noises? 
• Pull over if the light is flashing: A flashing light indicates a serious issue, such as a severe engine misfire that could damage the catalytic converter. Pull over safely and turn off the engine. Consider having the car towed. 

Next steps

• Get a diagnostic code read: Use an OBD-II scanner or visit an auto parts store or mechanic to have the trouble codes read. This will give you a specific error code to help diagnose the issue. 
• Address minor issues: If the problem is a simple one, like a loose gas cap, the light may go off on its own after it's been tightened. 
• Schedule a professional diagnosis: If the light remains on, schedule an appointment with a mechanic. The light can be triggered by a variety of problems, from a faulty sensor to a more significant engine issue. 

You can watch this video to learn how to reset the check engine light without a scan tool: 1mAuto EducateYouTube · Apr 14, 2025

Is the malfunction indicator light serious?

When the MIL illuminates, it means your vehicle's computer has sensed an issue. This could range from a minor problem, like a loose gas cap, to something more serious, like a malfunctioning sensor or engine component.