Tampering Q&A

What is tampering?

Tampering includes removing, bypassing, defeating, disconnecting, damaging, or in any way rendering ineffective any emissions control device—catalytic converter, air pump, and EGR valve—or element of design that has been installed on a motor vehicle or a motor vehicle engine, or having someone else do it for you. Tampering includes:

1. Disconnecting vacuum lines and electric or mechanical parts of the pollution control system, such as electrical solenoids, sensors, all or parts of the data link connector or vacuum-activated valves,

2. Adjusting any element of a car or truck’s emissions control design so that it no longer meets the manufacturer’s specifications,

3. 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.

Who does the prohibition of tampering with emissions controls apply to?

The federal Clean Air Act amendments of 1977 (Section 203(a)(3)), prohibits anyone from removing or rendering inoperative any emissions control device or element of design that is installed on a motor vehicle or a motor vehicle engine.

The prohibition against tampering applies to everyone, including vehicle owners, automobile repair facilities, commercial mechanics and fleet operators. It is also illegal for mechanics to advise customers on how to disconnect emissions controls.

Why is tampering prohibited?

Tampering with emissions controls is bad for air quality and public health. Motor vehicles contribute nearly half the total amount of man made air pollution in the U.S. today. For example in the Treasure Valley, 65% of the oxides of nitrogen are emitted from motor vehicles.

What impact does tampering with emission controls have on a vehicle?

Contrary to what you may have heard, tampering does not improve gas mileage, performance or driveability, and it sometimes makes them worse. Cars with catalytic converters get the same or better mileage than cars manufactured before catalytic converters were required. Tampering can also shorten an engine’s life and cause performance problems. In addition, tampering can void a vehicles warranty.

Are mechanics required to use manufacturer-made replacement parts?

No. Replacement parts may be rebuilt parts or equipment made by independent aftermarket parts manufacturers. Replacement parts must be at least equivalent in design and function to the parts that were originally on the car when it was certified. They must not have a negative effect on emissions control. To ensure replacement parts are acceptable, it is advisable to obtain written verification from the parts manufacturer that the part conforms in design and function with the original part.