Michigan Compiled Laws, Chapter 324. Natural Resources and Environmental Protection § 324.6504

Sec. 6504. (1) “Pollutants” means nitrogen oxides, carbon monoxide, hydrocarbons, and other toxic substances emitted from the operation of a motor vehicle.

(2) “Tamper with” means to remove or render inoperative, to cause to be removed or rendered inoperative, or to make less operative an emission control device or an element of an emission control device that is required by the clean air act to be installed in or on a motor vehicle.

(3) “Test cycle” means a 12-month period corresponding with the expiration date for registration of the vehicle.

(4) “Testing station” means a facility for motor vehicle inspection as provided in this part.