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Overview
All motor vehicles with internal combustion engines must have emissions control systems certified to legal standards. Tampering with these systems is prohibited by state and federal law. Tampering is defined as the disconnecting, deactivating, removing, modifying, or rendering inoperable any emissions control device or element of design that the manufacturer installed on or engineered into a motor vehicle. Tampering causes excess pollution and may cause damage to other emissions control devices on a vehicle. Tampering with emissions controls may void the vehicle’s warranty.
Tampering includes reprogramming the vehicle’s powertrain computer, often called re-flashing or installing a tune. This includes any software that would circumvent or defeat factory settings, disable check engine lights, or cause the vehicle to produce excessive exhaust smoke. Tampering also includes physical modifications to a motor vehicle such as installing an aftermarket exhaust system (pre-catalyst), installing a larger capacity turbocharger, or installing aftermarket exhaust headers. Deleting or removing any required emissions control component is tampering and is illegal.
The federal Clean Air Act (CAA) and Colorado Revised Statutes (CRS) include requirements to limit air pollution emissions from motor vehicles. Tampering with manufacturer-certified vehicles is illegal under CRS §25-7-144, CRS §42-4-314, and the federal CAA §203(a)(3). Manufacturers certify vehicles to meet federal standards or the more stringent California Air Resources Board (CARB) standards. In addition to tampering, CRS §25-7-144 also prohibits:
- Selling, offering for sale, possessing for sale, advertising, manufacturing, installing, or using any parts or software that modify the emissions control system of a motor vehicle.
- Selling, leasing, renting, or transferring title to (or offering to do any of these) a motor vehicle with an emissions control system that has been tampered with.
- Knowingly operating a motor vehicle that has an emissions control system that has been tampered with.
Tampering with motor vehicle emissions control systems is prohibited by state and federal law everywhere in Colorado. The emissions tampering laws apply to all motor vehicles, even those registered in an area that does not require periodic emissions inspections.
If you remove, disconnect, detach, deactivate, alter, modify, reprogram, interfere with, or reduce the effectiveness of any emissions control device installed by the manufacturer, or use replacement parts that do not meet the original equipment manufacturer’s specifications, then you are committing illegal tampering.
Buying or selling a motor vehicle
New vehicle dealers must not make any modification to a vehicle’s emissions control system before sale, so it is not necessary to have a new vehicle inspected before buying it. New gasoline-powered motor vehicles are exempt from emissions tests in the Automobile Inspection and Readjustment (AIR) program areas for the first seven years. New diesel-powered light and medium duty vehicles are exempt from Diesel Opacity Inspection Program (DOIP) inspections for four years.
Under Colorado law, sellers of used motor vehicles must provide the buyer with a passing emissions certificate. However, it is recommended for buyers to have the used vehicle inspected by a qualified repair facility for emissions compliance because, in certain cases, it is possible for a tampered vehicle to obtain a passing emissions test. Ask the inspector to check that the emissions control systems are all present and working properly. Having a shop verify perform a basic emissions control system inspection may prevent a failed emissions test or delays in getting the vehicle registered. Keep in mind that if the vehicle emissions control system has been tampered with, any remaining factory warranty may be void.
If a used vehicle that will require an emissions test to complete the registration is purchased from a licensed dealer, the dealer may provide a voucher redeemable for an emissions test instead of a passing emissions test certificate. If the purchaser uses the voucher at an emissions testing facility and the vehicle fails the test, the purchaser can return the vehicle to the dealer within five business days of the purchase. At that time the dealer must, at their option, repair the vehicle to pass the emissions test, cover the cost of repairs needed to pass the emissions test, or repurchase the vehicle at the purchase price. See CRS §42-4-309(6). Any of these options will fulfill the dealer’s responsibility for providing a passing emissions test but does not release responsibility for compliance with emissions tampering laws.
If sellers purchased a vehicle new, made no modifications to it, and had it serviced at reputable repair facilities, the vehicle is likely in compliance. If sellers purchased a vehicle used and don’t know its full history, they may want to have the vehicle checked at a qualified repair facility prior to selling it. If you sell a motor vehicle with tampered emissions controls you may be held responsible for repairing the vehicle.
Colorado state emissions inspection procedures are evolving and improving at detecting tampered vehicles. If you have a tampered vehicle that previously passed an emissions inspection, there is no guarantee it will pass again.
In addition to being responsible for the cost of returning a tampered vehicle to compliance, new laws in effect since Jan. 1, 2024 make it illegal to sell or transfer title to a tampered vehicle and include civil penalties for violations.
Emissions control system inspection basics
A trusted mechanic can inspect used vehicles for damage and check the emissions control system. Inspections can indicate if a used vehicle might need costly repairs or have difficulty passing an emissions inspection that could prevent buyers from getting the vehicle registered.
A repair shop can inspect a vehicle and help determine if the emission control system has been tampered with. A qualified technician will be able to check the following:
- Verify the correct catalytic converters are present on the vehicle and the Air Fuel Ratio (AFR) and oxygen sensors are properly installed in the correct locations. See the Aftermarket catalytic converter web page for more information.
- Note: The presence of a spacer on any of the sensors is an illegal tamper and also an indication that the catalytic converter(s) may be missing or in need of replacement.
- Verify the check engine light comes on with the ignition key on and goes off when the engine is running.
- Verify that all applicable On Board Diagnostic (OBD) system readiness monitors are enabled and have completed.
- Verify there is no visible smoke from the exhaust at any time. Older diesel powered vehicles may emit some visible smoke.
- Verify that no emissions relevant parts have been replaced with aftermarket or performance parts unless they have a CARB Executive Order (EO) exemption.
Simply because a part or software modification can be purchased in Colorado does not mean that it is legal for use in Colorado. - Verify that the engine control software has not been modified unless the software has a CARB Executive Order exemption.
Automotive professionals
Automotive technicians, repair shop owners, motor vehicle dealers, and fleet owners should be aware that the Colorado statute applies equally to all persons involved in tampering with a motor vehicle emissions system. Those who engage in tampering for profit or who own fleets are subject to more severe penalties.
To help avoid violations of the anti-tampering statute as an automotive professional or fleet owner:
- Do not remove, disconnect, detach, deactivate, alter, modify, reprogram or in any way change any emissions control device or element of design inoperable or less effective than originally designed or request that someone else do any of these things.
- Do not install customer provided parts that would result in a tampered emissions control system. You may be held personally responsible.
- Repair facilities may maintain or repair a tampered vehicle as long as you are not working directly on the tampered part. If the tampered part(s) needs to be repaired, replaced, or removed for access to other components, you must only install or reinstall compliant parts or else you must decline to perform the service.
- Do not advertise, install, sell, or possess for sale any non-compliant emissions control parts or defeat devices on/for any certified vehicle or engine.
- Use only emissions control system replacement parts that meet the OEM specifications or parts that are exempt by virtue of a CARB Executive Order.
- Be certain that the CARB Executive Order applies to the exact year, make, and model of the vehicle; CARB Executive Orders are very specific.
- Do not sell, rent, lease, or transfer title to a tampered motor vehicle.
- Under the Colorado statute, licensed dealers may engage in wholesale transactions but must bring a tampered vehicle back into compliance prior to offering it for retail sale.
- The Colorado statute does not invalidate the provisions of the Clean Air Act. The sale of a vehicle with a tampered emissions control system may still be a violation of federal law.
- Do not purchase or take a tampered vehicle as a trade-in from any person, dealer, or auto auction unless you will restore the vehicle to compliance prior to listing it for sale.
- When purchasing a vehicle with aesthetic modifications such as body kits or suspension changes, be aware of the increased possibility of tampering, especially engine control software modifications.
- Be aware that the seller of a motor vehicle in Colorado is legally responsible for providing a passing emissions inspection certificate. Sellers will be responsible for restoring any tampered vehicle to compliance.
Penalties
According to CRS §25-7-122(1)(b), the Colorado Department of Public Health and Environment has the authority to assess monetary penalties to any person who violates any requirements of an emissions control regulation of the Air Quality Control Commission. Any person who violates the anti-tempering provisions of CRS §25-7-144 is subject to civil penalties.
Individuals
For owners of nine or fewer vehicles who tamper with, knowingly operate, or transfer title to a tampered vehicle, Colorado civil penalties are up to $200 for a first offense, $500 for a second offense, and $1,200 for subsequent violations. Violations of the Colorado statutes also violate the federal Clean Air Act and can carry penalties of up to $3,750 for each part or component.
Businesses, dealers, and fleets
When any person or entity violates the anti-tampering statute for profit, the business, its owners and managers, service advisors, salespersons, and technicians who performed the work may each be held liable and subject to individual penalties.
Colorado civil penalties involving for-profit tampering are up to $1,000 for a first offense, $7,500 for a second offense, and $15,000 for subsequent violations. Violations of the Colorado statutes are also violations of the federal Clean Air Act and carry penalties of up to $37,500 for each part or component.
In addition to civil penalties under the anti-tampering statute, a motor vehicle dealer’s license may be denied, suspended, or revoked for selling a vehicle with a tampered emissions control system. See CRS §44-20-121(3)(S).
Frequently asked questions
Under the Colorado statute, tampering means to deactivate, dismantle, defeat, bypass, alter, modify, remove, or otherwise render inoperable, in whole or in part, physical or electrical parts or components of an emission control system. Any change to any part of a motor vehicle that will affect the performance of the emissions control system is considered tampering.
Vehicle owners, operators, automotive/diesel technicians and repair facilities, fleet managers, car and truck dealers, and auto/truck parts sellers anywhere in Colorado.
Emissions control system tampering is prohibited in all parts of Colorado and the prohibitions apply to all vehicles registered in the state, gasoline or diesel powered and light or heavy duty. The anti-tampering laws are applicable even for vehicles registered in an area that does not require periodic emission testing.
Tampering with motor vehicle emissions control systems is prohibited by federal law everywhere in the United States ,including Colorado.
CDPHE provides information about new emissions control tampering prohibitions under CRS §25-7-144 that went into effect on January 1, 2024. CDPHE contacts vehicle owners, fleet managers, vehicle dealers, parts sellers, and law enforcement agencies to clarify the new requirements. CDPHE also conducts enforcement activities to bring violators into compliance.
Here is a general list of things to do and to avoid:
- Do: Use only emissions control system replacement parts that are identical to the vehicle manufacturer’s parts or are specifically approved for your vehicle by the U.S. EPA or the CARB.
- Do: If you are modifying a vehicle with aftermarket performance or custom parts or software that affect the emissions control system, be certain that they are specifically approved for your vehicle by the U.S. EPA or CARB. Retain all documentation and purchase invoices with your vehicle records; the burden of proof of the legality of modifications lies with the vehicle owner.
- Do not: Remove, disconnect, detach, deactivate, alter, modify, reprogram or in any way render any emission control device or element of design inoperable or less effective than originally designed.
- Do not: Install any parts, accessories, or software that would result in tampering with the emissions control system of a motor vehicle.
- Do not: Operate any vehicle which you know has a tampered emissions control system.
- Do not: Sell, rent, lease, or transfer title to a vehicle with a tampered emissions control system.
A motor vehicle with a tampered emissions control system must be repaired to return it to the specifications certified by the manufacturer before it can be operated in Colorado. If a tampered vehicle fails an emissions inspection, the vehicle cannot receive a repair cost or hardship waiver. It must be returned to the certified configuration.
If you purchased a vehicle in a tampered condition, or a repair shop tampered with your emissions controls during a repair or service you can report the issue to the Air Pollution Control Division using the Vehicle Inspection Start online form, or call the state Emissions Technical Centers at (888) 861-2646.
Motor vehicles originally built for or converted into a vehicle used solely for competition use and not registered in any state are not subject to the anti-tampering statute CRS §25-7-144. Modifications made to competition-only vehicles are not subject to enforcement of CRS §25-7-144.
There are no exceptions for dual purpose (street/strip) vehicles. Any vehicle registered for on or off-road use in any state must comply with all Colorado and federal emissions control laws when present in Colorado. Switching between software calibrations or temporarily disconnecting/disabling parts that tamper with emissions control systems is not permitted.
Additional resources
If you suspect you have been impacted by illegal emissions control tampering you can report a potential emissions tamper.
Summaries of the Colorado anti-tampering statute (CRS 25-7-144):
- English summary for vehicle owners.
- Spanish summary for vehicle owners.
- English summary for repair shops.
- Spanish summary for repair shops.
- English summary for motor vehicle dealers.
- Spanish summary for motor vehicle dealers.
- English summary for parts sellers.
- Spanish summary for parts sellers.
Colorado has strict requirements for replacing catalytic converters. Learn more about aftermarket catalytic converter regulations.
Additional information on federal penalties. Updates for violations after Jan. 12, 2009.
EPA enforcement policy on vehicle and engine tampering and aftermarket defeat devices under the Clean Air Act. Contains more information about EPA enforcement policies.
Contact us
Questions? For gasoline-powered vehicles, email cdphe_detc@state.co.us. For diesel-powered vehicles email cdphe_dep@state.co.us. Contact CDPHE Emissions Technical Center staff at (888) 861-2646 for additional assistance with motor vehicle emissions tampering.
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