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Although Ohio’s vehicle anti-tampering law has been in effect for more than 25 years, vehicle owners, autobody shops, dealerships and auction houses are still being affected by tampered vehicles.

Tampering with a vehicle’s emissions control systems creates more air pollution and can result in high repair costs. Tampering can also negatively affect vehicle performance and void warranties.

So what’s illegal? According to Ohio Revised Code Section 3704.16, tampering means "to remove permanently, bypass, defeat, or render inoperative, in whole or in part, any emission control system that is installed on or in a motor vehicle." Tampering includes acts such as: removing the catalytic converter from a vehicle and installing a straight pipe; removing the substrate from inside the catalytic converter (cleaning it out); removing an air pump or disabling the air pump by removing the air pump belt; or installing a nonstandard thermostatic air cleaner.

The law enhances Ohio EPA’s authority to enforce existing tampering-related prohibitions such as selling or installing a device on a vehicle that would damage or bypass any emission control system. The prohibitions in the law apply to vehicles sold as is as well as those sold with warranties.

To help ensure that those affected understand their responsibilities, Ohio EPA’s Division of Air Pollution Control (DAPC) and Office of Compliance Assistance and Pollution Prevention (OCAPP) hosted a webinar on Oct. 2. This webinar defined illegal tampering and gave examples of different tampering scenarios. To view the recorded webinar, go to:

Violation could result in fines or felony charges. In 2018, an Ohio auto dealership was fined $40,000 for selling tampered vehicles. To request assistance, file a complaint or get more information visit or call (614) 644-2270.