Any aftermarket part that changes how a vehicle controls its emissions needs a CARB Executive Order before it can be sold, installed, or driven on public roads in California, and the requirements for a CARB Executive Order on aftermarket parts run from laboratory testing through a formal application, permanent labeling on the finished product, and ongoing compliance once the exemption is granted. The Executive Order, usually shortened to EO, is CARB’s formal finding that the part does not push tailpipe pollution past the vehicle’s original certification levels. No EO means the part is illegal, regardless of how well it is engineered.
Which Parts Actually Need an Executive Order
CARB splits aftermarket parts into two buckets, and only one of them needs an EO.
A replacement part is functionally identical to the original equipment in every way that affects emissions, including durability, under California Code of Regulations, Title 13, Section 1900.1Legal Information Institute. California Code of Regulations Title 13 Section 1900 – Definitions A direct-fit OEM-equivalent catalytic converter or oxygen sensor is a replacement part. No EO required.
An add-on or modified part changes the original configuration of the emission control system. Vehicle Code Section 27156 makes it illegal to install, sell, or even advertise such a part in California unless CARB has granted an exemption.2California Legislative Information. California Code Vehicle Code 27156 Title 13, Section 2222 adds a matching ban on advertising any device that alters the performance of a pollution control system without an EO.3Legal Information Institute. California Code of Regulations Title 13 Section 2222 – Add-On Parts and Modified Parts Anything that changes airflow, fuel delivery, ignition timing, or exhaust routing almost certainly lands in this bucket: cold-air intakes, headers, turbocharger kits, aftermarket catalytic converters, performance exhausts.
There is one narrow carve-out. Parts installed on true competition vehicles that never touch a public highway fall outside the EO requirement under Health and Safety Code Section 39048. Sellers relying on this exception have to keep sales records for at least four years and can expect CARB to look closely at whether the buyer actually had a race vehicle, whether an affidavit was signed, and whether sales volumes are consistent with the size of the racing community.4California Air Resources Board. Advisory 292 – Competition Vehicles and Performance Aftermarket Parts in California Selling “race only” parts in high volume without those safeguards is enforcement bait.
The Testing a Part Has to Pass
Before CARB will exempt a part, the manufacturer has to prove it does not increase emissions beyond the vehicle’s original certification levels. Title 13, Section 2222 requires laboratory evaluations following procedures the state board has formally adopted.3Legal Information Institute. California Code of Regulations Title 13 Section 2222 – Add-On Parts and Modified Parts
The core test is the Cold-Start CVS-75, a simulated driving cycle that measures hydrocarbons, carbon monoxide, and oxides of nitrogen from a cold engine start through city-style driving. The part passes only if measured pollutants stay within the limits the vehicle met at original factory certification.
Some parts also trigger Supplemental Federal Test Procedures, which simulate hard acceleration, sustained highway speeds, and air conditioning use. These matter for parts that mainly change engine behavior under heavy load, like turbocharger kits or performance exhaust manifolds. Testing is expensive and slow. There is no shortcut.
How to Apply for an Executive Order
Assemble the Documentation
Applications start at CARB’s website, where manufacturers download the exemption application form that matches the product type. Picking the right form matters from the beginning.5California Air Resources Board. ECCD/APCAB-001 On-Road Exemption Application for General Criteria Parts Form A The form asks for detailed information about the engine families the part is designed for, an engineering description of what the part does and how it interfaces with the emission control system, and all raw emissions data from laboratory testing.
The complete package also includes engineering drawings, installation instructions written for the end user, and a facsimile of the product information label. Every element of the modification has to be documented clearly enough that a CARB engineer who has never seen the product can understand exactly how it works, where it mounts, and what it changes. An incomplete package comes back, and each round-trip costs weeks.
Submission and Review
Completed applications go to CARB’s Monitoring and Laboratory Division, either through the electronic submission system or by mail. Staff runs a completeness check first. If everything is in order, a staff engineer is assigned to review the design and the supporting test data.
The review typically runs several months and has no guaranteed timeline. The assigned engineer may ask for clarification, revised documentation, or supplemental lab testing. When the evaluation is complete, the applicant receives a formal determination letter, and if the part meets all requirements, CARB issues the EO publicly. Novel designs and applications covering many vehicle families take longer.
Adding New Model Years to an Existing EO
When a vehicle carries over into a new model year without significant emissions-system changes, the manufacturer usually does not need to retest. CARB’s Category I process allows model-year additions to an existing EO without new laboratory work, as long as the part maintains the same design, fit, and function as the version already exempted.6California Air Resources Board. Category I – Model-Year Additions on Carryover Vehicles or Engines
The submission has to show the new model year’s emission control system has not changed in ways that would affect the part’s performance. That means an engineering analysis covering applicable emission standards, the worst-case vehicle previously tested, and any differences in the newer model year’s emissions hardware, plus a vehicle and engine coverage list in spreadsheet format with the new additions highlighted. Category I applications go to CARB’s aftermarket parts team by email and process faster than a full new-part application.6California Air Resources Board. Category I – Model-Year Additions on Carryover Vehicles or Engines
Labeling: The Part Has to Announce Itself
An EO on paper does not do a vehicle owner any good if a smog check technician cannot see it under the hood. Vehicle Code Section 27156 requires a permanent, visible label so technicians can verify the part is legal for the specific vehicle it is installed on.2California Legislative Information. California Code Vehicle Code 27156 The label carries the manufacturer’s name and the assigned EO number, formatted as D-XXX-XX.7California Air Resources Board. Understanding Catalytic Converter Labeling
The label has to survive the service life of the vehicle. Engine bays run hot, vibrate, and see oil and chemicals, so manufacturers typically use stamped metal plates or high-temperature industrial adhesive labels. Placement matters too. A technician has to be able to see the label without disassembling anything. A missing or illegible label can fail a smog check even when the part itself is legal.
What a Smog Check Actually Looks For
During a California smog inspection, the technician runs a visual check of the engine bay before any tailpipe testing. Any aftermarket component that modifies the emission control system, whether that is headers, an intake, or an exhaust piece, needs a visible EO number. If the technician sees a modified part with no EO label, the vehicle fails the visual portion immediately, and the tailpipe test does not run. EO numbers can be verified by smog check stations, Bureau of Automotive Repair referee stations, or by contacting CARB directly.8California Air Resources Board. Aftermarket, Performance, and Add-on Parts
For a vehicle owner, a part bought from a reputable manufacturer with a valid EO is straightforward at inspection time. A part installed without an EO fails, even if it does not actually raise emissions, and the vehicle cannot be registered until the modification is reversed or replaced.
Penalties for Selling or Installing Non-Exempt Parts
CARB enforces the aftermarket rules against manufacturers and against vehicle owners, and the numbers on the manufacturer side are much larger.
Health and Safety Code Section 43016 authorizes civil penalties of up to $37,500 per violation for anyone who violates Part 5 of Division 26, which includes the aftermarket parts rules, where no other specific penalty applies.9California Legislative Information. California Health and Safety Code Section 43016 For commercial vehicle owners and operators, Health and Safety Code Section 43008.6 allows CARB to collect up to $1,500 per violation of Vehicle Code Section 27156 covering specific tampering acts, including disabling fuel injection, catalytic converters, oxygen sensors, or evaporative control systems.10California Legislative Information. California Health and Safety Code Section 43008.6 CARB settlement agreements have reached tens of thousands of dollars against manufacturers caught selling non-exempted parts.11California Air Resources Board. Settlement Agreement – Power Products Unlimited, Inc.
For an individual owner, the practical penalty is the failed smog check. Without passing, the vehicle cannot be registered, which means it cannot legally be driven. The fix is returning the vehicle to a compliant setup or swapping in an EO-exempt alternative, plus paying for a re-inspection.
When CARB Can Pull an Executive Order
An EO is not permanent. Under Title 13, Section 2868, CARB’s Executive Officer can deny, suspend, or revoke a certification if the manufacturer misrepresented any material aspect of the application, used a label different from the approved version, or failed to comply with a CARB order.12Legal Information Institute. California Code of Regulations Title 13 Section 2868 – Denial, Suspension or Revocation Submitting false or incomplete information is grounds for revocation even if the manufacturer did not know it was wrong.
Revocation starts with certified mail notice explaining the reasons and supporting evidence. Suspension or revocation takes effect the moment the manufacturer receives the notice. The manufacturer can request a stay and a hearing, but CARB will deny the stay if the public health risk outweighs the business harm. Reinstatement requires correcting every issue identified in the notice and submitting a written report describing the corrective steps.12Legal Information Institute. California Code of Regulations Title 13 Section 2868 – Denial, Suspension or Revocation For an owner whose part loses its EO, the piece on the vehicle is no longer legal, and a compliant replacement may be needed to pass future smog checks.
Other States That Enforce CARB Rules
CARB EOs reach past California’s borders. Section 177 of the federal Clean Air Act allows any state with an approved air quality plan to adopt California’s vehicle emission standards, provided the state standards are identical to California’s and adopted at least two years before the model year they apply to.13Office of the Law Revision Counsel. 42 USC 7507 – New Motor Vehicle Emission Standards in Nonattainment Areas
As of early 2026, the jurisdictions that have adopted California’s vehicle regulations are Colorado, Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, and Washington D.C.14California Air Resources Board. States That Have Adopted California’s Vehicle Regulations In those states, the same EO requirements can apply to aftermarket parts. A part without an EO number on the label may be just as illegal in Portland or Denver as it is in Los Angeles, and manufacturers selling into any of these markets should treat the EO as the price of admission, not a California-only concern.