Is it OK to drive your car when the malfunction indicator lamp light turns on?

In most cases, you should not rely on the MIL as a signal to keep driving for long distances. If the light is flashing you should stop as soon as it is safe, while a steady light often allows for a brief trip to a shop but warrants prompt diagnosis. The exact risk depends on the underlying fault.

What the MIL can indicate

The malfunction indicator lamp (MIL), commonly known as the check engine light, signals that the vehicle’s on-board diagnostics system has detected a fault affecting the engine, emissions system or related components. The severity can range from a minor sensor issue to a misfire or a problem that could cause damage if ignored. A diagnostic trouble code (DTC) stored in the system guides technicians to the likely cause.

Common causes include:

• Loose or faulty gas cap


• Emissions control issues (EVAP system, purge valve or leak)


• Oxygen sensors (O2) or mass airflow sensor (MAF) problems


• Ignition system problems (spark plugs, ignition coils)


• Catalytic converter problems or inefficiency


• Wiring or sensor harness faults

Concluding: While some issues are minor and transient, many MIL triggers warrant a diagnostic scan to determine the exact fault and recommended fix. Driving decisions should be guided by the fault code and symptoms, not by the light alone.

Is it safe to drive?

Guidance depends on whether the MIL is steady or flashing. A steady light often indicates a fault that may not immediately impair safety but could affect performance, fuel economy, or emissions. A flashing light typically signals a severe condition, such as an engine misfire, that can damage the catalytic converter if you continue driving.

What to do if you must drive to a service facility:

• Plan the shortest, safest route and avoid heavy traffic if possible


• Drive at moderate speeds with gentle acceleration and steady engine load


• Keep an eye on engine performance, unusual noises, or loss of power


• Ensure you have enough fuel to reach a repair shop; if you notice worsening symptoms, stop and arrange assistance

Concluding: A steady MIL can often be tolerated for a short drive to a shop, but you should not treat it as a routine reminder to ignore a potential fault. A flashing MIL requires immediate attention and, if possible, towing rather than driving.

What to expect at the repair shop

When you bring the car in, technicians will diagnose the fault using a code reader and further tests to confirm the root cause. Expect a structured process that may include a review of live data and targeted inspections of relevant systems.

Typical diagnostic steps include:

• Read stored trouble codes with an OBD-II scanner


• Review freeze-frame and live data to identify contributing conditions


• Conduct visual inspections of ignition, fuel, exhaust, and emissions components


• Perform targeted tests (fuel trim, sensor inputs, compression, EVAP leak tests) as needed


• Repair or replace faulty parts and clear/reset the MIL, then verify by a drive cycle

Concluding: After the repair, the MIL should reset if the fault is fixed and the vehicle passes the diagnostic drive cycle. If the light returns, further diagnosis is required.

Tips to prevent the MIL from turning on

Regular maintenance and mindful fueling can reduce the odds of a lit MIL. Staying ahead of common failure modes helps protect emissions, efficiency, and reliability.

Preventive steps include:

• Follow the manufacturer’s maintenance schedule for spark plugs, sensors, and exhaust components


• Keep the gas cap tightened and replace if damaged; EVAP leaks are a frequent trigger


• Use quality fuel and avoid contaminated or low-grade fuel


• Address any drivability issues promptly to prevent collateral damage


• Have persistent or recurring lights diagnosed promptly to avoid catalytic converter damage

Concluding: Routine maintenance and timely diagnosis are the best defense against unexpected MIL illumination and costly repairs.

Summary

The malfunction indicator lamp signals faults in the engine, emissions system, or related components. A flashing MIL demands immediate stop and professional help, while a steady MIL usually warrants a prompt diagnostic and repair, but may allow a short drive to a shop. Always consult your owner’s manual and rely on professional diagnostics to confirm the exact cause and fix. Regular maintenance and quick attention to any symptoms help keep your vehicle running cleanly and safely.

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

Does the malfunction indicator light always mean major repair?

The malfunction indicator light may be indicating an issue that's easy to fix – like a loose gas cap that should be replaced. It could also be a signal of a severe issue that could ruin your engine components.

Can I drive with the Malfunction Indicator Lamp on?

You can typically drive with a steady or solid Malfunction Indicator Light (MIL), also known as the check engine light, but if the light is flashing, you should pull over immediately as it indicates a severe problem. A flashing light suggests a serious issue like a potential engine misfire that can cause expensive damage, particularly to the catalytic converter, so it's best to stop driving and call for assistance. 
This video explains what to do when your check engine light comes on: 58sTorqueCarsYouTube · Apr 24, 2023
If the light is steady (solid)

• It's generally safe to continue driving, but you should not ignore the light. 
• Address the problem as soon as possible to prevent more serious issues. 
• Check for simple fixes like making sure the gas cap is on tightly. 
• If you experience no other symptoms like rough idling, strange noises, or reduced power, you can likely drive to a mechanic or your home. 

If the light is flashing

• Pull over as soon as it is safe to do so and turn off the engine. 
• Do not drive the vehicle further. 
• A flashing light indicates a serious problem, such as an engine misfire, that requires immediate attention to avoid costly damage. 
• Call a tow truck to take your car to a mechanic. 

How much to fix a malfunction indicator light?

For 2022, CarMD found that the average check-engine light repair cost was $403, up 2.8% from 2021. The firm attributed the increase to rising parts costs related to supply chain issues and inflation.