How is my car tested for emissions?
Emissions testing is fast becoming the norm in the US as more and more states and counties recognize the need to control and monitor emissions and air quality. However, the emissions check process can be confusing (and it depends on your location as well as the age of the car you drive). How is your vehicle tested for emissions?
OBD system
The vast majority of test centers use your vehicle's on-board diagnostics (OBD) system for all or most tests. Of course, this varies from one location to another, and your test may involve more than an OBD system check.
To test the system, a tester will connect your vehicle's computer to a diagnostic scanner. This scanning tool is more powerful than those available to consumers and can provide a wealth of information about your vehicle's engine and exhaust system, as well as vital emissions components. After checking the OBD system, the tester will either let or let your vehicle down. However, another test may be required.
Exhaust pipe testing
An exhaust pipe test is done to measure the gases produced in your car's exhaust. Your vehicle may or may not require an exhaust pipe test - the test operator will tell you if your vehicle requires one. This is an important test because 1) your vehicle's OBD system does not monitor gases, and 2) your vehicle may be older than 1996 and not have an OBD II system.
Checking the gas cap
Some vehicles require the gas cap to be checked. This is a test to determine if the gas tank cap is properly sealed, or if the seal is broken and gas vapor is escaping from the tank, which is an additional source of contamination.
Visual inspection
Your vehicle may also need a visual inspection of the exhaust system. Again, the test administrator will let you know if a visual inspection is needed. This test is done to determine the physical condition of your exhaust system components that can be damaged by impact, salt, water and temperature fluctuations.
Your emissions testing process will vary depending on where you live in the country as well as the age of your vehicle. If you live in a very rural area or drive a hybrid or electric vehicle, you may not need an emissions test at all. Visit the websites of your state Department of Transportation or Department of Motor Vehicles for more information.
