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Enforcement & Citations
Regulation Text


California identified particulate matter (PM) emissions from diesel-powered engines as a toxic air contaminant (TAC) based on its potential to cause cancer, premature death, and other health problems. The mission of California Air Resources Board’s (CARB) Enforcement Program is to protect the environment and public health and provide safe, clean air to all Californians by reducing emissions of toxic air contaminants through the fair, consistent and comprehensive enforcement of air pollution laws, and by providing training and compliance assistance.

CARB adopts regulations to control diesel PM emissions and focuses on achieving compliance with diesel regulation requirements across the full range of regulated vehicles and equipment, especially in communities near highways, ports, and other high traffic areas that are disproportionally affected by diesel PM emissions. Our Enforcement Policy describes CARB’s authority for enforcement; processes for pursuing enforcement and determining penalties in individual enforcement actions; resources for compliance assistance; responsibility to the public and especially disadvantaged communities; public communication; and information protection.

Enforcement is critical to ensure the public health benefits of CARB programs, and helps to maintain a level playing field across each regulated industry. CARB’s goal is to achieve comprehensive compliance with every regulation it adopts. A critical component of the diesel enforcement program is having field inspectors across the state inspect trucks and other equipment for compliance with CARB’s diesel programs, such as the Heavy-Duty Vehicle Inspection Program, Statewide Truck and Bus (applies if based out of state), Transport Refrigeration Unit, Solid Waste Collection Vehicle, Drayage Truck, , and Tractor-Trailer Greenhouse Gas programs. Field inspectors also conduct inspections for compliance with Public Agencies and Utilities (PAU), In-Use Off-Road, Commercial Vehicle Idling, and School Bus Idling regulations. CARB’s Enforcement Program has a successful model of finding violators. Violations of the requirements of Diesel Airborne Toxic Control Measures (ATCM) and Heavy-Duty Diesel Vehicle Inspection Program (HDVIP) can result in written citations with penalties identified below.



  • 2025 TRUCK & BUS
ATCM regulations are codified in the California Code of Regulations (CCR) and developed to reduce TACs. CARB is responsible for developing statewide programs and strategies to reduce the emission of smog-forming pollutants and toxics by diesel-fueled mobile sources. Diesel emissions contain various harmful TACs including polycyclic aromatic hydrocarbons, benzene, formaldehyde, acetaldehyde, acrolein, and 1,3-butadiene. Diesel mobile source ATCMs assist in achieving this mission by creating enforceable requirements that aim to reduce the emissions associated with mobile sources.

To Clear an ATCM Citation: A citation notification letter will be sent to the responsible party by mail with instructions on how to clear the citation. Within the citation due date stated in the citation notification letter, you must do the following:
  • Pay the penalty stated in the citation notification letter
  • Provide proof that the vehicle or fleet has been brought into compliance with the violated regulation (with the exception of CVI citations).

  • 2183 TAMPERING
The HDVIP program requires heavy-duty trucks and buses to be inspected for excessive smoke, tampering, and engine certification label compliance. Any heavy-duty vehicle traveling in California, including vehicles registered in other states and foreign countries, may be tested. CARB inspection teams perform tests at border crossings, CHP weigh stations, fleet facilities, and randomly selected roadside locations. Owners of trucks and buses found in violation are subject to penalties. To Clear an HDVIP Citation:
A citation notification letter will be sent to the responsible party by certified mail with instructions on how to clear the citation. Within the citation due date stated in the citation notification letter, you must do the following:

    Pay the civil penalty as set forth in 13 CCR 2180-2189 and provide proof of correction as follows:
  • For Emission Control Labels, provide a copy of the invoice from the engine dealer that clearly shows that a new label has been installed on the cited vehicle.
  • For Excessive Smoke, provide a passing opacity test, or documentation showing transfer of vehicle ownership if the vehicle has been sold, or documentation showing that the vehicle is non-operational if it has been junked.
  • For Tampering, a copy of a valid repair order showing which parts were replaced to correct the violation.

If you have questions about an ATCM or HDVIP citation received pertaining to any of the programs listed above, and the citation number begins with three letters, such as TRU, ORE, CVI, ECL, T01, T02, S01, S02, DTR, PAU, REF, SBI, SWC, STB, NOV or GHG you may contact the Diesel Hotline at 1-866-6DIESEL (1-866-634-3735).

Penalties and Sanctions

Failure to comply with CARB regulations can result in penalties and sanctions. Penalties are designed to remove any economic benefit a responsible party obtained through noncompliance and to deter future violations across the industry. While maximum penalties are established by statute, CARB measures the severity of the violation by considering all relevant circumstances including the eight statutory factors together with general considerations that apply to all penalty determinations. By consistently applying the enforcement process, CARB strives to assess an appropriate penalty that is fair to the responsible party, and is just to the impacted community and the affected public. For more information regarding CARB’s penalty policy, please view CARB’s Enforcement Policy.

Truck & Bus Regulation

In 2018, CARB began a streamlined enforcement process for the Truck and Bus Regulation to increase outreach to owners of heavy-duty diesel trucks. The streamlined process involves sending a Notice of Non-Compliance to heavy-duty diesel vehicle owners that have older vehicle models that could potentially be out of compliance with applicable emission standards as outlined in the regulation. Once the notice has been sent, the vehicle owners are given the opportunity to provide documentation demonstrating that the vehicle in question is compliant with the requirements of the Truck and Bus Regulation. If compliance is not demonstrated, the vehicle will be deemed non-compliant and a DMV registration hold could potentially be placed on the vehicle.

Engine/Emission Control Labels (ECL)

Several CARB diesel regulations require specific engine information, such as engine model year (MY) and engine family name, which is available from the emission control label (ECL) that is attached to your vehicle.

Existing California law (AB 1009 of 2004) requires vehicles that operate in California, regardless of entry point, to run with engines that meet emissions standards at least as stringent as U.S. federal standards for the model year that the engine was manufactured. All heavy-duty vehicles need to have proof that the engine meets appropriate emissions standards by having the manufacturer ECL properly affixed on the engine.

The ECL must be legible, maintained at the location originally installed by the engine manufacturer, and correspond to the engine serial number stamped on the engine. CARB's Enforcement Division has an ADVISORY regarding ECL requirements.

  • Engine Family Name:
    The engine family name (may also be called engine family name or emission family name/number) is a 10 to 12 character alpha-numeric code assigned by the engine manufacturer that allows specific engine certification information to be determined. It can be found on the engine control label (ECL). If your ECL is missing or illegible you should contact your local dealer or engine manufacturer to obtain the engine family information and to order a replacement label. Be sure to have your engine serial number available.

    Example engine families: TCP629EZDARM or 2DDXH12.7FGF
    The engine family name is typically required for reporting with CARB and unique to an engine of a specific model year, build, and manufacturer. The engine family name is not the engine manufacturer, engine model or serial number. The oldest engines may have an engine family name only a few characters long.

    If you have an engine’s displacement, manufacturer and model year, the Retrofit Device Verification Database may be useful to help determine the Family Name.

  • Engine Manufacturer:
    The engine builder is typically different than the vehicle manufacturer. The photos below do not have the manufacturer on them, but yours will.

  • Engine Model Year:
    The engine model year is also on the ECL. Contact your local engine dealer or the manufacturer to get a replacement label should yours be missing or illegible—you will need to provide your engine serial number to obtain the model year AND to have the label replaced. Typically, the engine model is one year older than the chassis model year. For example, a 2007 vehicle typically has a 2006 model year engine installed.

    If you own a rebuilt or remanufactured engine, please note that while rebuilt engines keep their original identity and engine serial number, remanufactured engines may lose their original serial number and will instead have an engine label identifying it as a remanufactured engine. Please contact your local installer, dealer, and/or manufacturer for more information.

    A standard rebuilt engine is considered the same emissions level as the original configuration. For example, if a 1996 model year engine was rebuilt in 2011, it would still be considered a 1996 model year engine.

    Also, please note that you cannot replace your engine with an engine older than the original manufactured date. For example, if your original vehicle was manufactured with a 2006 engine, you cannot replace the 2006 engine with a 2005 engine.

  • Engine Model Year Vs. Vehicle Model Year:
    A common mistake when reporting equipment information to CARB is to use the same model year for both the truck/bus body and the engine when they are different. Engines are manufactured separately from the vehicle chassis and are certified to meet the standards for the year of manufacture. Due to this, engines are often certified to an earlier model year than the truck body. CARB regulations typically designate requirements based on engine model year so it is important to determine an engine's specific model year by checking the ECL.

  • OEM PM Filter:
    An original equipment manufacturer (OEM) particulate matter (PM) filter is installed primarily on 2007 MY and newer engines. To determine if you have an OEM PM filter you can check the ECL for the and acronyms DPF or PTOX, although this may not be definitive. Additional confirmation of an OEM PM filter on your engine can be made by checking the exhaust system or looking for PM filter specific lights in the dash. A final way to determine the existence of an OEM PM filter is to look up the engine certification for your engine to determine if the engine was certified to the 0.01 g/bhp hr standard for PM.
For examples and detailed instructions on where to find this, please view our Emissions Control Label webpage.


The Notices of Non-Compliance and Notices of Violations are letters sent in efforts of this streamlined enforcement process for the Truck and Bus Regulation. If you have received a letter that has a six digit tracking number beginning in “NC” or “NV”, the letter is one of the previously mentioned notices. If you have any questions in relation to this notice please contact 866-634-3735 or email with your “NC” or “NV” number in the subject line.