2004 Subaru Impreza Owner's Manual - Page 276

Starting and operating State emission testing (U.S. only) At state inspection time, remember to tell your inspection or service station in advance not to place your Subaru AWD vehicle on a two-wheel dynamometer. Otherwise, serious transmission damage will result. Some states have started using dynamometers in their state inspection programs in order to meet their obligation under federal law to implement stricter vehicle emission standards to reduce air pollution from cars. A dynamometer is a treadmill or roller-like testing device that allows your car's wheels to turn while the car remains in one place. Depending on the severity of a state's air pollution problems, the states must adopt either a "basic" or "enhanced" vehicle emission inspection test. Normally, a portion of the basic emission test consists of an emission inspector inserting an analyzer probe into the exhaust pipe of an idling vehicle for a short period of time. States with more severe air pollution problems are required to adopt an enhanced vehicle emission test. This test simulates actual driving conditions on a dynamometer and permits more accurate measurement of tailpipe emitted pollution than the basic emission test. The U.S. Environmental Protection Agency (EPA) and states using two-wheel dynamometers in their emission testing programs have EXEMPTED Subaru AWD vehicles from the portion of the testing program that involves a two-wheel dynamometer. There are some states that use four-wheel dynamometers in their testing programs. When properly used, that equipment will not damage an AWD Subaru vehicle. Under no circumstances should the rear wheels be jacked off the ground, nor should the driveshaft be disconnected for state emission testing. Testing of an All-Wheel Drive vehicle must NEVER be performed on a single two-wheel dynamometer. Attempting to do so will result in uncontrolled vehicle movement and may cause an accident or injuries to persons nearby. Resultant vehicle damage due to improper testing is not covered under the SUBARU Limited Warranty and is the responsibility of the state - CONTINUED - 7-7