Can I drive my car if it says check emission system?

You can typically drive for short trips when the Check Emission System light is on, but you should not ignore it. The warning signals an emission-control fault that may affect performance and fuel economy, and it can eventually lead to failed emissions tests or damage if left unresolved.

Understanding what the warning means

In most modern vehicles, the Check Emission System light is part of the onboard diagnostics (OBD-II) system. It illuminates when sensors detect a fault in the emissions-control system or related engine management components. The range of potential causes goes from simple (like a loose gas cap) to complex (such as a faulty catalytic converter).

Common causes

Here are the most frequent reasons this warning appears.

• Loose, cracked, or missing gas cap


• Faulty oxygen sensors or catalytic converter problems


• Engine misfire or fuel-air mix issues (spark plugs, ignition coils, injectors)


• Malfunctioning mass air flow sensor or intake leaks


• EVAP system valve or purge valve problems


• Vacuum leaks or other emissions-control hardware faults

Many of these issues are repairable, and some are minor (like a loose gas cap). Others require diagnostic work to identify the exact faulty component. A professional should confirm the root cause and the necessary repairs.

Is it safe to drive right now?

The safety of driving depends on whether the light is steady or flashing and whether you notice symptoms in the car’s performance. A steady light with normal engine operation often allows a cautious trip to a repair shop. A flashing light or symptoms such as rough idling, misfires, reduced power, or strong fuel smell indicate a higher risk of damage and require immediate attention. If you experience any of these, stop safely and seek help rather than continuing to drive.

Guidelines if you see the light

Follow practical steps to assess the situation before continuing to drive more than necessary to reach a repair facility.

• Check the gas cap: ensure it’s tight and in good condition; replace it if damaged or missing.


• Note any symptoms: rough running, misfires, poor acceleration, or unusual odors.


• Use an OBD-II scanner to retrieve diagnostic trouble codes (DTCs) if you have access, and share them with a technician.

These steps help you avoid unnecessary repairs and give your mechanic a clearer starting point for diagnosis.

What to do next

Once you’re able to, arrange a professional diagnosis and follow their repair recommendations. Emissions-related issues can range from simple maintenance to component replacement, and addressing them promptly can prevent further damage and ensure your vehicle remains compliant with emissions testing where required.

What you can expect at the shop

A technician will typically diagnose the fault with codes, inspect related components (EVAP system, sensors, ignition, fuel system, catalytic converter), and may perform tests to reproduce the issue. Repairs may include replacing a faulty sensor, repairing EVAP valves, or, in some cases, catalytic converter work.

Regular maintenance and timely fixes help keep your car cleanly running and within emissions standards, reducing the chance of breakdowns and test failures.

Summary

Bottom line: You can usually drive briefly if the light is steady, but don’t ignore the Check Emission System warning. Start with simple checks like securing the gas cap and retrieving diagnostic codes, then have a qualified mechanic identify and repair the fault. Prompt attention can prevent further damage, preserve fuel efficiency, and help ensure you pass emissions testing when applicable.

Can I drive with the check emission system light on?

Some common issues that trigger the warning light include a loose gas cap, a clogged air filter, a bad catalytic converter, a failing oxygen sensor, and other faulty engine sensors. You can still drive with an illuminated check emission light, but it's not recommended as it could lead to engine damage.

Can you drive a car with emissions issues?

Can I still drive my car with the “Check Emission System” warning light on? It's not recommended to drive with the Check Emission System warning light on until you know the cause. Long-lasting damage and extensive repairs can result.

How do you get your car to pass emissions?

To get your car to pass emissions, perform routine maintenance like changing the oil and air filter, address the "Check Engine" light, and drive the car to a warm-up it before the test. You can also use a fuel system cleaner and make sure all fluids are at their proper levels. Properly inflating your tires and ensuring your gas cap is on tightly can also improve your chances of passing. 
This video explains several tips for passing an emissions test, including warming up the engine and using premium fuel: 55sRatchets And WrenchesYouTube · Dec 1, 2015
Before the test

• Fix the "Check Engine" light: A car will not pass with this light illuminated. Clear the code with a scan tool and repair the issue before the test. 
• Complete routine maintenance: Change your oil, replace the air filter, and replace spark plugs if needed. This ensures the engine is running efficiently. 
• Check all fluids: Make sure all fluid levels are correct before the test. 
• Inspect the gas cap: Ensure the gas cap is not loose or cracked, as this can cause emissions-related codes. 
• Add fuel additives: Use a fuel system cleaner to help clean out deposits in the fuel system and potentially improve emissions. 
• Properly inflate tires: Correct tire pressure reduces rolling resistance on the rollers used in the emissions test. 

Just before and during the test 

• Warm up the engine: Drive your car for at least 15-20 minutes before the test, including some highway driving, to ensure the engine and catalytic converter are at their optimal operating temperatures. 
• Remove excess weight: Clear out any unnecessary items from your car, especially the trunk, as excess weight can add load to the engine during the test. 
• Go to the test center with the right amount of fuel: Having a gas tank that is between a quarter and three-quarters full can help the test run smoothly. 

This video demonstrates how to properly warm up your car before an emissions test, including checking the catalytic converter: 1mDannys DIY GarageYouTube · Jul 14, 2025
After a failure

• Address any specific error codes: If the car fails, use a scan tool to read the specific trouble codes and make the necessary repairs. 
• Complete a drive cycle: After repairs, you may need to drive the car for a specified number of miles (often 60-120) under various conditions to reset the vehicle's emissions monitors before retesting. 

You can watch this video to learn how to reset the drive cycle monitors and get your car ready for a smog check: 1mVincent StevensonYouTube · Sep 28, 2022

Is the emission system problem bad?

Yes, an emissions system problem can be bad because it may lead to decreased fuel efficiency, poor engine performance, increased pollution, and potential long-term engine damage. Ignoring a "Check Engine" or emissions light, especially if it's flashing, can cause further damage and lead to costly repairs. It can also cause your vehicle to fail emissions tests and may result in fines. 
You can watch this video to learn about common causes of emissions system problems: 1mFixITYouTube · Apr 6, 2025
Potential consequences of an emissions system problem

• Decreased fuel economy: A malfunctioning system can cause your engine to work harder, leading to more frequent stops at the gas pump. 
• Poor engine performance: You may notice sluggish acceleration, rough idling, or a general loss of power. 
• Environmental harm: The vehicle will likely release more harmful pollutants into the atmosphere. 
• Engine damage: Driving with an emissions problem can cause further wear and tear on your engine and other components, potentially leading to major, expensive repairs down the line. 
• Failure to pass emissions tests: Your vehicle will not pass mandatory emissions inspections, which can prevent you from registering it. 

What to do if you see an emissions warning light

• For a steady light: It's not an emergency, but the issue should not be ignored. Schedule a diagnostic inspection with a mechanic as soon as possible. 
• For a flashing light: This indicates a more severe problem. Do not drive the vehicle if possible and have it towed to a mechanic to prevent further damage. 
• For any emissions issue: Drive as little as possible until the problem is diagnosed and fixed. 

This video explains what to do if you see an emissions warning light: 31sVehicle FreakYouTube · Oct 24, 2022