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The California Air Resources Board (CARB or Board) will conduct a public hearing at the date and time noted below to consider approving proposed amendments to the On-Road Heavy-Duty Engine and Vehicle Omnibus Regulation, the Low Carbon Fuel Standard (LCFS), and to propose permanently adopting the Emergency Vehicle Emissions Regulations that CARB previously noticed as an emergency rulemaking on September 15, 2025.
CARB is proposing these Omnibus amendments, LCFS amendments, and permanent adoption of its Emergency Vehicle Emissions Regulations together as one rulemaking for administrative efficiency, but the Omnibus and Associated Amendments, LCFS Amendments, and Emergency Vehicle Emissions Regulations are three separate regulatory items proposed for approval.
Date: November 20, 2025
Time: 9:00 a.m.
Location: California Environmental Protection Agency
California Air Resources Board | Byron Sher Auditorium
1001 I Street, Sacramento, California 95814
Remote Option: Zoom
This public meeting may continue at 9:00 a.m. on November 21, 2025. Please consult the public agenda, which will be posted ten days before the November 20, 2025, Board Meeting, for important details, including the day on which this item will be considered and how the public can participate via Zoom if they choose to be remote.
Background
1. Proposed regulatory action to amend the Omnibus Regulation:
The proposed regulatory action to amend the Omnibus regulation would largely align most of the requirements for new 2027 and subsequent MY HDEs with the corresponding provisions of the EPA-NOx rule. CARB staff proposes to align the following Omnibus requirements for HD compression-ignition and spark-ignition engines with the corresponding EPA-NOx rule:
• Certification emissions standards and test procedures for criteria pollutants including NOx, PM, carbon monoxide and hydrocarbons;
• Merging the California-Averaging, Banking, and Trading (ABT) program with the federal-ABT program;
• Durability demonstration provisions;
• UL and warranty periods for mileage, years, and hours; and
• HD in-use testing program including the two-bin moving average window analysis methodology and the off-cycle standards with some differences in the interim compliance allowance and the ambient temperature adjustment factor.
CARB staff is also proposing to end the applicability of the transit agency diesel-fueled bus and engine exemption request process beginning with the 2027 MY.
a. Proposed regulatory action to amend the On-Board Diagnostic (OBD) Regulations:
CARB staff is also proposing the following amendments to the OBD regulations:
• Updates to the definitions of the Federal Test Procedure cycle and the Supplemental Emission Test cycle;
• Modifications to the engine aging requirements for durability demonstration testing of medium-duty engines (MDE) and HDEs;
• Adoption of alternate, higher malfunction criteria, higher nonconformance criteria, and more relaxed test-out criteria for OBD monitors to account for the proposed lower Federal Test Procedure non-methane hydrocarbon and carbon monoxide standards for 2027 and subsequent MY MDEs and HDEs; and
• Adoption of new data stream parameters required to be made available on HDEs.
Additionally, to address manufacturers’ implementation concerns and improve CARB staff’s review of OBD applications, CARB staff is proposing the following amendments:
• Modifications to the NOx sensor monitor compliance criteria to address issues with the current criteria;
• Modifications to the in-use monitor performance denominator incrementing criteria for monitors that are part of a multiple NOx converting catalyst system to address issues of possible low in-use monitoring frequency;
• Modifications to the criteria to be exempt from monitoring the catalyzed PM filter non-methane hydrocarbon conversion capability to address implementation issues;
• Modifications to the criteria to set the readiness status for a readiness group to “complete” to address monitors that do not run frequently in-use;
• Substitution of the not-to-exceed bin with the new two-bin moving average window bins for NOx emission tracking (i.e., the REAL requirements) in order to align with the binning method used for tailpipe in-use compliance testing;
• Changes to manufacturer self-testing engine selection criteria and testing deadlines for HDEs to account for the updated full UL mileage requirements;
• Delay to the implementation date of the final in-use monitor performance ratio for the PM filter monitors on light-duty vehicles and engines and medium-duty vehicles and MDEs; and
• New required CARB templates for manufacturer submission of OBD information and test data to standardize data and information submitted by manufacturers and help CARB staff review the data and information.
CARB staff is also proposing several amendments to the OBD regulations to correct errors and to align with the in-use emission warranty information and reporting (EWIR) requirements.
b. Proposed regulatory action to amend the EWIR Requirements and Corrective Action Procedures
Furthermore, to address issues that have arisen within the EWIR program, CARB staff is proposing the following amendments to the EWIR requirements and corrective action procedures:
• Failure levels triggering recall and corrective action for 2027 and subsequent MYs;
• Allowing manufacturers to collect new owner information using alternative methods for vehicles that are subject to corrective action;
• Changing the proof of correction requirements for over-the-air recalls; and
• CARB no longer requires recall repair labels for recalls that only involve software reflashes.
2. Proposed regulatory action to make permanent the Emergency Vehicle Emissions Regulations:
CARB proposed its Emergency Vehicle Emissions Regulations to maintain protective emission standards for vehicles and engines while ensuring manufacturers can sell vehicles and engines into California despite the emergency the federal government has created by issuing illegal and unconstitutional congressional resolutions targeting its waivers.
To ensure that new motor vehicles can continue to be sold in California, despite the ongoing uncertainty introduced by the federal government into the State’s longstanding regulatory program, CARB staff is proposing to amend its regulations to clarify that the criteria pollution provisions of the LEV III regulation remain operative, with the caveat that CARB may enforce Advanced Clean Cars II, to the extent permitted by law, in the event a court of law holds invalid the resolution purporting to disapprove that waiver. CARB staff is thus proposing to make permanent its Emergency Vehicle Emissions Regulations.
CARB staff is similarly proposing to make permanent its Emergency Vehicle Emissions Regulations amendments to the medium- and heavy-duty regulations to clarify that the pre-Omnibus provisions remain operative, with the caveat that CARB may enforce the Omnibus regulation, to the extent permitted by law, in the event a court of law holds invalid the resolutions purporting to disapprove that waiver.
CARB continues to accept and process certification applications for the LEV IV and Omnibus emission standards. Hence, both sets of standards will be present in the California Code of Regulations during this period of unprecedented uncertainty. Regulated parties may choose to follow either the Advanced Clean Cars II or Omnibus standards or the older pre-ACC II and pre-Omnibus provisions. Regulated parties, however, assume the risk of non-compliance if they choose to certify only to the older provisions, and the congressional resolutions disapproving the waivers of federal preemption under the Clean Air Act are declared invalid.
CARB may also consider other changes to the sections affected, as listed on page 2 of the notice, or other sections within the scope of this notice, during the course of this rulemaking process.
3. Proposed regulatory action to amend the LCFS Regulation:
To increase opportunities for near-term, low-emission electrification solutions to provide electricity vehicle fueling while charging station operators work with utilities to connect their sites to electricity distribution systems, CARB staff is proposing to allow the use of indirect accounting of renewable natural gas (RNG) for LCFS reporting and crediting of electricity for vehicle charging produced by linear generators. This proposal may increase the near-term availability of low-carbon intensity electricity for electric truck refueling.
Inquiries concerning the substance of the proposed Omnibus regulatory action may be directed to the agency representative Daniel Hawelti, Staff Air Pollution Specialist, On-Road Heavy-Duty Diesel Section, at (951) 542-3195 and daniel.hawelti@arb.ca.gov or (designated back-up contact) Mitzi Magtoto, Staff Air Pollution Specialist, On-Road Heavy-Duty Diesel Section, at (279) 208-7363 and mitzi.magtoto@arb.ca.gov.
Inquiries concerning the substance of the proposal to make permanent CARB’s Emergency Vehicle Emissions Regulations may be directed to the agency representative Kim Heroy-Rogalski, P.E., Chief, Mobile Source Regulatory Development Branch, California Air Resources Board, (279) 208-7792, kim.heroy-rogalski.@arb.ca.gov.
Inquiries concerning the substance of the proposed LCFS regulatory action may be directed to the agency representative Dillon Miner, Staff Air Pollution Specialist, Industrial Strategies Division, at 279-208-7437 and dillon.miner@arb.ca.gov.
The Notice, ISOR, and all subsequent regulatory documents are available on CARB's Rulemaking webpage.
Written Comment Period & Comment Submittal
In accordance with the Administrative Procedure Act, interested members of the public may present comments orally or in writing during the hearing and may provide comments by postal mail or by electronic submittal before the hearing. The public comment period for this regulatory action will begin on September 26, 2025. Written comments not submitted during the hearing must be submitted on or after September 26, 2025, and received no later than November 10, 2025. Comments submitted outside that comment period are considered untimely. CARB may, but is not required to, respond to untimely comments, including those raising significant environmental issues. The Board also encourages members of the public to bring to the attention of staff, in advance of the hearing, any suggestions for modification of the proposed regulatory action. Comments submitted in advance of the hearing must be addressed to one of the following:
Clerk of the Board, California Air Resources Board
1001 I Street, Sacramento, California 95814
Please note that under the California Public Records Act (Government Code section 6250 et seq.), your written and oral comments, attachments, and associated contact information (e.g., your address, phone, email, etc.) become part of the public record and can be released to the public upon request.
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