Will Your Car Pass Emissions with Check Engine Light On?: 1 Minute to Understand Emissions Testing and Check Engine Light Issues

Whether your car will pass an emissions test with the check engine light on is a common concern for many drivers preparing for annual inspections. Generally, if your check engine light is illuminated, your vehicle will not pass the emissions test in most states. This warning light signals that your car’s onboard diagnostic system (OBD-II) has detected a problem related to the emissions, engine, or other crucial systems. During an emissions inspection, technicians connect to your car’s OBD-II port to check for error codes and system readiness. If the light is on, it typically means your car’s emission control system isn’t functioning properly, automatically resulting in a failed inspection until the underlying issue is resolved and the codes are cleared.

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If your check engine light turns on close to your inspection date, schedule a diagnostic check as soon as possible. Fixing minor issues early can save you from repeat inspections and additional fees.

FAQ

Q: Can I pass an emissions test if the check engine light is on but the car seems to drive fine?

A: No. Most states automatically fail vehicles with an illuminated check engine light, regardless of how well the car drives.

Q: What should I do if my check engine light is on before my emissions test?

A: Have your vehicle diagnosed and repaired, then drive for several days to ensure the system resets, and the light stays off before re-testing.

Q: How long does it take for the check engine light to reset after a repair?

A: After the repair, your car may need to complete several driving cycles (which can vary from a few miles to over 100, depending on the vehicle) before the light turns off and the system passes the readiness check.

Q: Can auto parts stores help diagnose check engine codes for emissions problems?

A: Yes, many auto parts stores offer free OBD-II scans and can provide you with the trouble codes affecting your emissions system.

Q: Will disconnecting the battery turn off my check engine light for the emissions test?

A: While disconnecting the battery can temporarily reset the light, the system’s “readiness monitors” will also reset, which can cause an automatic fail if they aren’t complete when tested.