United States	EPA 420-F-93-003
Environmental Protection September 1993
Agency
Air And Radiation (6406J)
EPA Mechanics:
An Important
Law That
Affects You
Don't Tamper
With Emissions
Controls!

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Don't Tamper With Emission
Controls!
Do you repair, service, lease, sell or trade motor vehi-
cles or motor vehicle engines? Do you operate a
motor vehicle fleet? If you do, a law against tamper-
ing with emission controls applies to you.
As of November 15,1990, federal law prohibits
anyone from removing or rendering inoperative any
emission control device or element of design that is
installed on a motor vehicle or a motor vehicle
engine. Anyone who breaks this law can be penalized
as much as S2,500 for each motor vehicle or motor
vehicle engine they tamper with. Dealerships and
manufacturers can be penalized up to S25.000 for
each violation. This prohibition is one of the 1990
Amendments to the U.S. Clean Air Act.
The purpose of the law is to make sure that cars
meet Federal emission standards. If you don't com-
ply, the result will be dirtier air, a loss in fuel econo-
my, and possibly fines.
What Is Tampering?
You are tampering if you remove, bypass, defeat,
disconnect, damage or in any way render ineffective
any emission control device or element of design
that has been installed on a motor vehicle or a motor
vehicle engine, or have someone else do it for you.
Tampering includes:
•	Removing such devices as the catalytic converter,
air pump and EGR valve, or doing anything to
them to keep them from working properly.
•	Disconnecting vacuum lines and electrical or
mechanical parts of the pollution control system,
such as electrical solenoids, sensors or vacuum-
activated valves.
*	Adjusting any element of a car or truck's emission
control design so that it no longer meets the man-
ufacturer s specifications.
*	Installing a replacement part that is not the same
in design and function as the part that was
originally on the vehicle, such as an incorrect
exhaust part.
*	Adding a part that was not originally certified on
the car, such as installing a turbocharger.
You can avoid making innocent mistakes that could
be tampering, if you simply make all adjustments
according to the manufacturers specifications, and
install parts designed to properly replace the origi-
nal parts.
Why Do We Need An
Antitampering Law?
Motor vehicles contribute nearly half the total
amount of man-made air pollution in the United
States today. They emit nearly sixty percent of the
total amount of carbon monoxide, a poisonous gas.
They also emit one fourth of the hydrocarbons and
nearly one-third of the oxides of nitrogen. These two
substances are major causes of the unhealthy smog
that hangs over so many cities and suburbs.
Congress has established emission standards for
cars and trucks to reduce this pollution and protect
the .American public's health. Car manufacturers are
required to certify that their designs meet these
standards.
Tampering changes a vehicle's certified design
and causes it to exceed emission standards. EPA sur-
veys show that tampering is widespread. Some ser-
vice and repair shops even claim that removing
emission controls improves gas mileage, which is not
true. To put an end to tampering, and to make sure

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that cars meet emission standards for as long as they
are being driven, Congress broadened the antitam-
pering provision of the Clean Air Act.
What Is The Antitampering Law?
The original law was part of the Clean Air Act of
1970. It applied only to manufacturers and car deal-
ers. This law still applies to between 20,000 and
30,000 new car dealers and manufacturers, who may
have to pay as much as $25,000 for each car they
tamper with.
The antitampering law was expanded by the
1977 Clean Air Act Amendments to apply to all
automobile repair facilities, commercial mechanics,
and fleet operators. These facilities can be penalized
up to S2.500 for each motor vehicle or motor vehicle
engine that they tamper with.
The 1990 Clear Air Act Amendments broad-
ened the tampering provision even further, and it
now applies to everyone, including car owners. Any-
body who tampers can be penalized up to 52,500 per
car or truck. Many states also impose additional
fines.
Does Tampering Improve Gas
Mileage And Driveability?
No! Tampering does not improve gas mileage, per-
formance or driveability, and it sometimes makes
them worse. In cars that were manufactured after
1974, the catalytic converter is the primary means
of emission control. These devices do not decrease
gas mileage or driveability. Cars with catalytic con-
verters get the same or better mileage than cars
made before they were being used.
The pollution control systems used on cars since
the mid-1970 s have contributed to a dramatic
improvement in fuel economy. If you damage or dis-
connect the catalytic converter, all you accomplish is
to increase air pollution and waste an expensive piece
of equipment.
Tampering can shorten an engine's life and also
cause performance problems. In todays cars, emis-
sion control is part of the total design and function
of many of the engine's components. This includes
all parts of the fuel, ignition and air management
system, intake and exhaust manifolds, and the EGR
valve. When the emission control design of one of
these systems or components is changed, perform-
ance will likely suffer. Often, the result is loss of fuel
efficiency and increased emissions. Maintenance,
fuel system adjustments, ignition timing, compres-
sion ratio, and EGR can all affect how long the
engine will last. You can shorten the engine's life and
worsen its performance if you tamper.
Can Tampering Void A Cars
Warranty?
Yes! Under the Clean Air Act, car manufacturers
must provide warranties that cover emission control
systems and devices. But if you tamper with the
emission controls, the manufacturer may not have to
honor the warranty. (These warranties may also be
void if leaded gas is used in cars that require unlead-
ed fuel.)
When an owner whose car has been tampered
with discovers that the dealer won't honor the war-
ranty, he or she may complain to federal authori-
ties. When the complaint is investigated, the repair
shop and the mechanic that did the tampering
could be exposed and prosecuted.

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Do Mechanic Have To Use
Replacement Parts That Are
Made By The Manufacturer?
No. You may also use rebuilt parts, or equip-
ment made by independent aftermarket parts
manufacturers.
Replacement parts must be equivalent in design
and function to the parts that were originally on the
car when it was certified. They must not have a nega-
tive effect on emission control. To be certain you're
using acceptable replacement parts, get a written
statement from the parts manufacturer, saying that
the replacement part conforms in design and func-
tion with the original part.
When you install an aftermaket catalytic con-
verter be sure you fulfill all the requirements of EPAs
aftermarket catalytic converter policy. For informa-
tion concerning this policy, please read EPA's pam-
phlet, "Aftermarket Catalytic Converters: Guide to
Their Purchase, Installation, and Use."
Is The Public Being
Informed About The
Antitampering Law?
Yes, but many car owners still think they can get bet-
ter gas mileage and driveability by removing or dis-
connecting emission controls. Some owners try to
do it themselves, but others ask their automobile
mechanic to tamper.
To prevent this, the Environmental Protection
Agency has launched a public information pro-
gram about the antitampering law, and the penalty
for tampering. Consumers are being told that tam-
pering won't improve fuel economy or perfor-
mance, and might make them worse. Since pollu-
tion controls on new cars cost about S500, tamper-
ing is an expensive waste.
When a mechanic refuses to tamper with a car,
the customer may ask for advice on how to discon-
nect emission controls. You and your customer are
both at risk if you give such advice. Tampering by a
car owner is against the federal law and is also pro-
hibited by state law in most states.
What Can I Do To Help?
You can help keep the air clean by refusing to tamper
with emission controls, and by learning how to
properly service and maintain emission control sys-
tems. All work done on cars should be performed
according to manufacturer's specifications.
If you have more questions about the antitam-
pering law, contact the U.S. Environmental Protec-
tion Agency, Field Operations and Support Division
(6406J), Washington, DC 20460 (telephone 202-
233-9100).

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