Emissions Tampering Fines: Federal, Criminal, and State Penalties

Emissions tampering fines under the federal Clean Air Act run up to $59,114 per vehicle for manufacturers and dealers and up to $5,911 per incident for individual vehicle owners and mechanics, based on the inflation-adjusted civil penalty caps in effect as of January 2025. Those numbers are per violation, and each vehicle, engine, or defeat device counts separately, so the total exposure for a shop or fleet can climb into six or seven figures quickly. State fines, voided warranties, and mandatory vehicle restoration land on top of the federal amount.

What Tampering Actually Means

The Clean Air Act prohibits removing or disabling any emission control device or design element installed to meet federal regulations. Before a vehicle’s first sale, no one may alter those controls at all. After the sale, the removal or disabling has to be done “knowingly” to be a violation, though that standard is easy to meet in practice.¹

Typical examples: removing a catalytic converter, disabling the exhaust gas recirculation system, gutting a diesel particulate filter. Software counts too. Reprogramming an engine control module to change fueling or emissions behavior, often called tuning, is treated the same as removing hardware. A tune that hides emissions faults from the onboard diagnostic system is a straightforward violation.²

The statute separately prohibits manufacturing, selling, or installing defeat devices — any part whose principal effect is to bypass or disable emission controls, where the seller knows or should know how it will be used. This is the provision that sweeps in delete-kit sellers, aftermarket tuning companies, and the shops that install their products.¹

How the Federal Numbers Add Up

The base statutory penalties in the Clean Air Act are $25,000 per violation for manufacturers and dealers and $2,500 for everyone else. The Federal Civil Penalties Inflation Adjustment Act requires the EPA to raise those caps annually. As of the January 2025 adjustment, the caps are $59,114 for manufacturers and dealers and $5,911 for other individuals per tampering event or defeat device sale.³

Every vehicle or engine is a separate violation, and every defeat device manufactured, sold, or installed is a separate offense.⁴ A shop that deleted emissions equipment on 50 trucks faces a theoretical ceiling near $300,000 in federal civil penalties alone. A company selling thousands of tuning devices faces exposure in the millions. In 2024, engine manufacturer Cummins agreed to pay $1.675 billion in combined federal and state civil penalties for emissions control violations, with an additional $326 million for mitigation and vehicle recalls.⁵

Reporting and recordkeeping violations carry the same $59,114 cap and can be assessed for each day the violation continues.³

How the EPA Sets Your Actual Fine

The statutory caps are ceilings, not sticker prices. The statute directs the EPA or a court to weigh the gravity of the violation, any economic benefit the violator gained from noncompliance, the size of the business, compliance history, steps taken to fix the problem, the effect of a large penalty on the violator’s ability to stay in business, and anything else justice requires.⁴

The EPA’s mobile source penalty policy splits the calculation in two. The economic benefit component strips out every dollar the violator saved or earned by breaking the rules — the net profit from selling illegal products, or the avoided maintenance and parts costs for a fleet that ran with deleted equipment. The gravity component starts with a base tied to engine size, then gets multiplied for how egregious the conduct was (major, moderate, or minor) and how many vehicles or engines were involved. Removing a catalytic converter outright scores higher than a minor calibration issue. Knowing about a violation for years and doing nothing pushes the number up; remediation and cooperation bring it down.⁶

Criminal Exposure

The Clean Air Act includes criminal provisions on top of the civil ones. Knowingly tampering with, falsifying, or failing to install a required monitoring device or method carries up to two years in prison and criminal fines, doubled for a second conviction. Broader knowing violations, including false statements in required reports, carry up to five years, again doubled for repeat offenders.⁷

Between fiscal years 2020 and 2023, the EPA completed 17 criminal cases related to aftermarket defeat devices, producing $5.6 million in penalties and 54 total months of incarceration.⁸

Federal criminal enforcement changed in 2025. The Department of Justice directed federal prosecutors to stop pursuing criminal charges for emissions defeat device tampering, taking the position that these violations can be pursued only as civil offenses. The directive affected more than a dozen pending criminal cases and roughly 20 open investigations. The EPA separately told its staff to stop investigating or making criminal referrals for emissions control software tampering. The underlying criminal statutes and the civil penalties remain on the books, so a future administration could restart criminal enforcement without any change to the law.

State Fines and Inspection Consequences

Most states prohibit emissions tampering under their own laws, and many enforce those laws through mandatory inspection and registration programs. The details vary, but the pattern is consistent: a tampered vehicle fails its emissions test, registration cannot be renewed until the problem is fixed, and fines apply for the failed inspection or the tampering itself.⁹

State fines for individual vehicle owners are typically lower than federal ones, ranging from a few hundred to a few thousand dollars per violation. Commercial violations, negligent air contamination, and fraudulently issued passing inspection reports draw much steeper amounts in some states, and in aggressive air quality programs repeat commercial violations can trigger penalties of tens of thousands of dollars per day. Some states also bar the sale or registration of tampered vehicles.⁹

Where inspection programs allow a compliance waiver, owners have to spend a minimum amount on attempted repairs first. Those thresholds typically fall between $100 and over $1,400 depending on the state. Standard inspection fees run from free to about $35.

Warranties and Mandatory Restoration

Removing or disabling emission controls can void the manufacturer’s warranty on the affected components, and some insurers exclude coverage for tampered vehicles and engines. A blown turbo or an engine failure that would ordinarily be a warranty claim becomes an out-of-pocket repair if the manufacturer determines emissions equipment was altered.⁹

EPA enforcement actions routinely require violators to restore tampered vehicles to their original certified emissions configuration. For a repair shop, that means reinstalling catalytic converters, particulate filters, and associated sensors on every vehicle it modified, at the shop’s expense. In large settlements, companies also face mandatory recall programs costing hundreds of millions on top of the civil penalty.⁵

Cutting the Penalty Through Self-Disclosure

The EPA’s Audit Policy offers a substantial reduction for entities that find violations on their own and come forward. Meeting all nine conditions produces a 100% cut of the gravity-based portion of the civil penalty, leaving only the economic benefit component (which the EPA will waive if it is insignificant), and no criminal prosecution recommendation to the Department of Justice.¹⁰

The nine conditions are strict. The violation has to be found through a systematic audit or compliance management system, not through a government investigation or third-party tip. The entity has to disclose in writing within 21 days of discovery and correct the problem within 60 days. The violation cannot repeat one that occurred at the same facility in the past three years, and it cannot have caused serious actual harm or imminent endangerment. Full cooperation is required throughout. Entities that satisfy every condition except systematic discovery still qualify for a 75% reduction of gravity-based penalties.¹⁰

Federal enforcement has historically focused on companies that make, sell, and install defeat devices rather than on individual vehicle owners. A shop selling diesel delete kits or an online retailer shipping tuning software is far more likely to draw EPA attention than a single truck owner. The statutory authority to fine individuals up to $5,911 per tampering event is still available and has been used.¹¹ For most individual owners, the more common financial hit comes from failed state inspections, registration holds, and voided warranties.

1
Office of the Law Revision Counsel. 42 USC 7522 – Prohibited Acts
2
Clean Air Northeast. Tampering and Aftermarket Defeat Devices
3
eCFR. 40 CFR 19.4 – Statutory Civil Monetary Penalties, as Adjusted for Inflation, and Tables
4
Office of the Law Revision Counsel. 42 USC 7524 – Civil Penalties
5
United States Environmental Protection Agency. 2024 Cummins Inc. Vehicle Emission Control Violations Settlement
6
United States Environmental Protection Agency. Clean Air Act Mobile Source Civil Penalty Policy
7
Office of the Law Revision Counsel. 42 USC 7413 – Federal Enforcement
8
United States Environmental Protection Agency. Stopping Aftermarket Defeat Devices for Vehicles and Engines
9
U.S. Environmental Protection Agency. Enforcement Alert – Aftermarket Defeat Devices and Tampering are Illegal
10
United States Environmental Protection Agency. EPA’s Audit Policy
11
United States Environmental Protection Agency. Clean Air Act Vehicle and Engine Enforcement Case Resolutions