Vehicle tampering 101

It's illegal to tamper with gas and diesel vehicles. Motor vehicles contribute nearly half of air pollution in the U.S., emitting nearly sixty percent of carbon monoxide, a quarter of hydrocarbon pollution, and nearly a third of nitrogen oxide pollution. 

What is vehicle tampering?

Tampering is when someone removes, disconnects, alters, damages or in any way renders ineffective any pollution-control equipment installed in a motor vehicle, or installs a device that overrides pollution control equipment. For example, a tampered vehicle may:

  • Be missing such devices as a properly operating catalytic converter, air pump or exhaust gas recirculation (EGR) valves, diesel particulate filter (DPF), etc
  • Contain an aftermarket programmer or chip that disables pollution control equipment
  • Contain an emission control design that is different from the vehicle manufacturer’s specifications
  • Contain a knowingly installed replacement part affecting the pollution control equipment that is not equivalent in design and function to the original part 
  • Have a part not originally certified for the vehicle (for example, dual carburetors installed to replace a single unit)

Tampering may include, but not be limited to, acts such as removing the catalytic converter, ‘drilling out’ or rendering the diesel particulate filter inoperable, or installing a ‘programmer’, ‘tuner’, or ‘chip’ that overrides pollution control devices.

What does the law say?

The 1990 amendments to the federal Clean Air Act do not allow anyone to tamper with a vehicle’s emission controls unless the individual is making necessary changes or repairs (Section 203 (a) (3) A and B). In addition, most of the 50 states have similar prohibitions about automotive tampering.

  • Anyone selling a vehicle in the state must certify, in writing, that the vehicle has all its proper pollution control equipment. (Minn. Stat. 325E.0951)
  • No one can operate, sell, or transfer title of any motor vehicle unless the emission controls are in place and working properly. (Minn. Rule 7023.0120)

Because new owners become responsible for recently purchased vehicles if they are discovered to be missing pollution control equipment at a later date, vehicle buyers should inspect their purchases thoroughly. (Actions you can take if you bought a vehicle with a tampered emission control system.)

Why do people tamper with vehicles?

Some people still believe that tampering with a car’s emission controls will improve the vehicle’s performance. Others simply don’t realize the importance of repairing or replacing pollution control devices. Here are some other commonly held myths about automotive tampering:

Adjusting my car to something other than the manufacturer's specifications will improve a car's gas mileage

FACT: Changing the manufacturer's recommended settings for the engine may actually reduce fuel efficiency. Today's automakers design cars to meet the best possible balance between performance, mileage and low emissions. Tuning your car to the manufacturer's specifications will maximize the engine's performance and save fuel. 

Installing a programmer, tuner or chip in my vehicle will enhance my car’s performance

FACT: While a chip/programmer/tuner might increase performance at high RPM’s the sacrifice can be a LOSS of power under other conditions and many times can have an adverse effect on drivability. This means in exchange for slightly increased power during a small fraction of the time, you will be sacrificing overall performance and drivability.

Pollution controls on cars don't work and have little effect on improving air quality

FACT: Vehicles with proper emission controls are largely responsible for reducing smog, carbon monoxide and nitrogen oxide pollution in urban areas. Vehicles with proper emission-control devices can reduce their emissions by 90 percent. 

Tampering will not affect my car's warranty 

FACT: Under the Clean Air Act, car manufacturers are required to provide a warranty covering emission control devices for five years or 50,000 miles, whichever comes first. However, when a car's emission controls have been tampered with, the manufacturer will not honor the vehicle's warranty.

There is no punishment for tampering with my car's emission control devices 

FACT: Federal and state laws do not allow tampering with emission control equipment. Violation of these laws could result in stiff fines and/or imprisonment