UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
ENGINE SWITCHING FACT SHEET
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460

March 13, 1991

OFFICE OF AIR AND RADIATION

Pursuant to frequent requests for information received by the U.S. Environmental Protection Agency
(EPA) regarding the legality and effects of engine switching, this document will summarize federal law
and policy pertaining to this matter, and will discuss other related issues.

A. Federal Law
The federal tampering prohibition is contained in section 203(a)(3) of the Clean Air Act (Act), 42
U.S.C. 7522(a)(3). Section 203(a)(3)(A) of the Act prohibits any person from removing or rendering
inoperative any emission control device or element of design installed on or in a motor vehicle or motor
vehicle engine prior to its sale and delivery to an ultimate purchaser and prohibits any person from
knowingly removing or rendering inoperative any such device or element of design after such sale and
delivery, and the causing thereof. The maximum civil penalty for a violation of this section by a
manufacturer or dealer is $25,000; for any other person, $2,500. Section 203(a)(3)(B) of the Act
prohibits any person from manufacturing or selling, or offering to sell, or installing, any part or
component intended for use with, or as part of, any motor vehicle or motor vehicle engine where a
principal effect of the part or component is to bypass, defeat, or render inoperative any device or
element of design installed on or in a motor vehicle or motor vehicle engine, and where the person
knows or should know that such part or component is being offered for sale or is being installed for
such use. The maximum civil penalty for a violation of this section is $2,500.
EPA received many questions regarding the application of this law to a situation where one engine is
removed from a vehicle and another engine is installed in its place. EPA's policy regarding "engine
switching" is covered under the provisions of Mobile Source Enforcement Memorandum No. lA
(Attachment 1). This policy states that EPA will not consider any modification to a "certified
configuration" to be a violation of federal law if there is a reasonable basis for knowing that emissions
are not adversely affected. In many cases, proper emission testing according to the Federal Test
Procedure would be necessary to make this determination.

A "certified configuration" is an engine or engine chassis design which has been "certified" (approved)
by EPA prior to the production of vehicles with that design. Generally, the manufacturer submits an
application for certification of the designs of each engine or vehicle it proposes to manufacture prior to
production. The application includes design requirements for all emission related parts, engine
calibrations, and other design parameters for each different type of engine (in heavy-duty vehicles), or
engine chassis combination (in light-duty vehicles). EPA then "certifies" each acceptable design for use,
in vehicles of the upcoming model year.
For light-duty vehicles, installation of a light-duty eng~ne into a different light-duty vehicle by any
person would be considered tampering unless the resulting vehicle is identical (with regard to all
emission related parts, engine design parameters, and engine calibrations) to a certified configuration of
the same or newer model year as the vehicle chassis, or if there is a reasonable basis for knowing that
emissions are not adversely affected as described in Memo 1A. The appropriate source for technical
information regarding the certified configuration of a vehicle of a particular model year is the vehicle
manufacturer.
For heavy-duty vehicles, the resulting vehicle must contain a heavy-duty engine which is identical to a
certified configura- tion of a heavy-duty engine of the same model year or newer as the year of the
installed engine. Under no circumstances, however, may a heavy-duty engine ever be installed in a
light-duty vehicle.
The most common engine replacement involves replacing a gasoline engine in a light-duty vehicle with
another gasoline engine. Another type of engine switching which commonly occurs, however, involves
diesel powered vehicles where the diesel engine is removed and replaced with a gasoline engine.
Applying the above policy, such a replacement is legal only if the resulting engine-chassis configuration
is equivalent to a certified configuration of the same model year or newer as the chassis. If the vehicle
chassis in question has been certified with gasoline, as well as diesel engines(as is common), such a
conversion could be done legally.
Another situation recently brought to EPA's attention involves the offering for sale of used foreign-built
engines. These engines are often not covered by a certified configuration for any vehicle sold in this
country. In such a case, there is no way to install such an engine legally. EPA has recently brought
enforcement actions against certain parties who have violated the tampering prohibition by performing
illegal engine switches.
It should be noted that while EPA's policy allows engine switches as long as the resulting vehicle
matches exactly to anv certified configuration of the same or newer model year as the chassis, there are
some substantial practical limitations to performing such a replacement. Vehicle chassis and engine
designs of one vehicle manufacturer are very distinct from those of another, such that it is generally not
possible to put an engine into a chassis of a different manufacturer and have it match up to a certified configuration. Therefore, practical considerations will generally limit engine switches to installation of
another engine which was certified to be used in that same make and model (or a "twin" of that make
and model, e.g., Pontiac Grand Am and Oldsmobile Calais). In addition, converting a vehicle into a
different certified configuration is likely to be very difficult, and the cost may prove prohibitive.


B. State Laws
Many states also have statutes or regulations prohibiting tampering in general. Most of these laws
specifically prohibit tampering by individuals. A few specifically prohibit engine switching, using
provisions similar to those stated in EPA's policy. To determine the state law in any given state, the
state's Attorney General's office should be contacted. In addition, many states have state or local
antitampering inspection programs which require a periodic inspection of vehicles in that area, to
determine the integrity of emission control systems. Many programs have established policies for
vehicles which have been engine switched. While EPA does not require these programs to fail engine
switched vehicles which are not in compliance with federal policy, the Agency does strongly
recommend that these programs set their requirements so as to be consistent with the federal law. State
or local programs which pass illegally engine switched vehicles may mislead federally regulated parties
into believing that engine switching is allowed by federal law.