Federal penalties for emissions tampering run up to $5,911 per violation for an individual vehicle owner and up to $59,114 per vehicle for a manufacturer, dealer, or shop, under the most recent inflation-adjusted schedule effective January 8, 2025.1eCFR. 40 CFR Part 19 – Adjustment of Civil Monetary Penalties for Inflation Each vehicle counts as its own offense, and each defeat device sold counts separately for parts sellers, so the exposure for a business scales fast. The fines are only the start: warranty denials, insurance disputes, failed state inspections, and a vehicle you can’t legally resell all follow from the same conduct.
The Federal Prohibition Behind the Fines
The penalties enforce 42 U.S.C. § 7522(a)(3). Before a vehicle’s first sale, no one may remove or disable any emissions-related device installed to meet federal regulations. After the sale, the same rule applies to anyone who “knowingly” does so. A separate clause makes it independently illegal to manufacture, sell, offer to sell, or install any part whose principal effect is to bypass or defeat an emissions control device, as long as the seller knows or has reason to know the part will be used that way.2Office of the Law Revision Counsel. 42 USC 7522 – Prohibited Acts
Every vehicle sold in the United States holds a certificate of conformity for a specific configuration. Any modification that pushes the vehicle outside that configuration is a compliance problem, even if the owner believes the change is harmless.3Environmental Protection Agency. Overview of Certification and Compliance for Vehicles and Engines
What Actually Triggers a Penalty
Tampering covers any action that degrades or circumvents a vehicle’s certified emissions controls. The EPA draws no meaningful distinction between low-tech and high-tech methods.
Physical modifications are the classic cases: disconnecting vacuum hoses, removing catalytic converters, gutting diesel particulate filters, plugging exhaust gas recirculation passages. Any physical removal or alteration of a factory-installed emissions component qualifies, regardless of the owner’s reason.
Software counts too. The EPA treats the calibrations inside an engine control unit as part of the certified emissions configuration, and specifically defines “required emission controls” to include “calibrations that manage fueling strategy and other operations in the engine itself.”4U.S. Environmental Protection Agency. National Enforcement and Compliance Initiative: Stopping Aftermarket Defeat Devices for Vehicles and Engines A performance tune that alters the air-fuel ratio is a federal violation if it changes the certified emissions profile, even with the exhaust hardware intact. Tuning companies that sell those calibrations face liability for manufacturing and selling defeat devices.
Diesel delete kits sit squarely in the enforcement crosshairs. These kits reprogram the ECU through the onboard diagnostics port so the engine stops monitoring the DPF and diesel exhaust fluid system, often paired with a replacement exhaust pipe that bypasses the filter. Marketing may emphasize fuel economy and lower maintenance, but installing a delete kit on a vehicle used on public roads violates the Clean Air Act.5National Agricultural Law Center. DOJ and EPA Clarify Stance on Diesel Vehicles Under the CAA
The EPA has also said its safe harbor for modifications that don’t affect emissions does not extend to conduct affecting onboard diagnostic systems. Disabling a check engine light or installing a sensor simulator can trigger enforcement even when the underlying emissions hardware is untouched.6Environmental Protection Agency. EPA Tampering Policy: Enforcement Policy on Vehicle and Engine Tampering
How the Fines Are Calculated
The statutory base penalties under 42 U.S.C. § 7524 are $25,000 for manufacturers and dealers and $2,500 for individual vehicle owners, per violation. Those figures adjust annually for inflation. Under the current schedule, the maximums are $59,114 per vehicle for manufacturers and dealers, and $5,911 per violation for individuals.1eCFR. 40 CFR Part 19 – Adjustment of Civil Monetary Penalties for Inflation
The multiplier is what makes business-side exposure so severe. Each vehicle or engine counts as a separate offense for manufacturers and dealers, and each defeat device sold counts as a separate offense for parts sellers.7Office of the Law Revision Counsel. 42 USC 7524 – Penalties A shop that sold delete kits for 500 trucks is looking at 500 counts, each valued up to $59,114. That math is why EPA enforcement actions against defeat-device sellers routinely settle in seven figures.
COBB Tuning, a well-known performance tuning manufacturer, entered a consent decree requiring a $2,914,000 civil penalty and a permanent prohibition on manufacturing or selling aftermarket defeat devices. The company was permitted to keep selling products covered by a California Air Resources Board Executive Order confirming they don’t increase emissions.8U.S. Environmental Protection Agency. COBB Tuning Products, LLC Clean Air Act Settlement
The EPA designated “Stopping Aftermarket Defeat Devices” as a National Enforcement and Compliance Initiative for fiscal years 2020 through 2023 and resolved dozens of civil cases in that window. The agency’s focus remains on the manufacturing and supply side, though individual owners are not exempt.4U.S. Environmental Protection Agency. National Enforcement and Compliance Initiative: Stopping Aftermarket Defeat Devices for Vehicles and Engines
The 2026 Criminal-Charge Change
On January 21, 2026, the Department of Justice announced it would no longer bring criminal charges under the Clean Air Act based on tampering with onboard diagnostic systems in motor vehicles. The DOJ found persuasive a legal argument that OBD systems monitor the emissions control system rather than emissions themselves, and therefore don’t qualify as “monitoring devices” under the criminal penalty provision at 42 U.S.C. § 7413(c)(2)(C).5National Agricultural Law Center. DOJ and EPA Clarify Stance on Diesel Vehicles Under the CAA
The change does not make tampering legal. Civil penalties under 42 U.S.C. § 7524 still apply to every violation, and the DOJ and EPA have said they will continue civil enforcement. What went away is criminal prosecution risk for one specific category of conduct.
The Costs That Aren’t Fines
Even if you never draw an EPA case, tampering hits the wallet in other ways.
Warranty
The Magnuson-Moss Warranty Act (15 U.S.C. § 2302) blocks manufacturers from conditioning a warranty on the use of a specific brand of part, so a dealer can’t void your warranty because you installed aftermarket brake pads or an air filter.9Office of the Law Revision Counsel. 15 USC 2302 – Rules Governing Contents of Warranties Emissions modifications are different. If you install a performance tune or delete an emissions component and your engine or turbocharger later fails, the manufacturer can deny coverage by showing the modification caused or contributed to the failure. Magnuson-Moss protects your right to use aftermarket parts, not your right to a warranty payout when altered parts change how the vehicle operates. A deleted diesel truck with a cracked turbo housing is likely to see a warranty denial, and the manufacturer will be on solid ground.
Insurance
The EPA has noted that tampered vehicles may not be covered by insurance policies.10Environmental Protection Agency. Tampering and Defeat Devices: What You Need to Know Insurers commonly include material modification clauses that let them deny claims on vehicles substantially altered from factory specifications without disclosure. An undisclosed emissions deletion can give an insurer grounds to dispute coverage after an accident or a mechanical failure.
Resale and Registration
Selling a tampered vehicle exposes you to the same Clean Air Act prohibitions that apply to parts sellers. Transferring a truck with deleted emissions equipment means offering to sell a product with a defeat device. Many states also prohibit registering tampered vehicles, and a vehicle that can’t pass a state emissions inspection is effectively unsellable in the states that require one. Restoring a deleted diesel truck to its certified configuration with OEM parts often runs several thousand dollars, and the parts aren’t always readily available for older models.
State Inspection Consequences
Roughly 29 states require some form of emissions testing as a condition of registration or renewal. A vehicle with a deleted catalytic converter, gutted DPF, or reflashed ECU will fail, and the owner can’t legally register or drive it until the problem is fixed.
Most inspection states offer a repair waiver for vehicles that fail despite good-faith repair efforts. Waiver thresholds vary and generally range from around $100 to over $1,000 in documented emissions repair spending. Waivers exist for legitimate mechanical failures, not for deliberate tampering. A deleted truck that fails because its DPF was removed doesn’t qualify, because restoring illegally removed equipment isn’t a repair.
“Off-Road Only” and “Competition Use” Labels
Aftermarket catalogs are full of products labeled “for off-road use only” or “for competition use only.” The labels don’t create a legal safe harbor. The EPA’s position is that a motor vehicle certified under the Clean Air Act must stay in its certified configuration even if the owner later uses it solely for racing, and there is no federal process to reclassify a street-titled vehicle as a competition vehicle to escape emissions law. The agency stated in a 2015 rulemaking that “certified motor vehicles and motor vehicle engines and their emission control devices must remain in their certified configuration even if they are used solely for competition or if they become nonroad vehicles or engines.”10Environmental Protection Agency. Tampering and Defeat Devices: What You Need to Know
As a practical matter, the EPA has said it generally exercises enforcement discretion for owners who can show a vehicle is used exclusively for competition and never driven on public roads. Enforcement discretion is a policy choice, not a legal right, and it offers no protection to the companies selling the parts. The RPM Act (Recognizing the Protection of Motorsports Act) has been introduced in Congress multiple times to explicitly legalize emissions modifications on vehicles converted for competition, and as of 2026 it has not been signed into law.11Congress.gov. S.2736 – RPM Act of 2021
If a Business Has Already Sold Defeat Devices
A shop that discovers it may have sold or installed defeat devices has a path to reduced penalties through voluntary self-disclosure. Entities that discover violations, promptly disclose them through the EPA’s eDisclosure system, and move quickly to correct the problem may be eligible for a reduction or elimination of civil penalties.10Environmental Protection Agency. Tampering and Defeat Devices: What You Need to Know
Self-disclosure works best when the violation is genuinely inadvertent and the business acts before the EPA does. A shop that knowingly sold thousands of delete kits and then self-reports after reading about an enforcement sweep is unlikely to get the same treatment as one that discovers a single employee was installing uncertified parts without authorization.