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Step 1
Learn about the test. OBD II refers to the testing most states conduct for vehicle emissions. It is also known as smog testing. The test is based on the emission levels your vehicle emits when it is running; the results must comply to state standards.
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Step 2
Study your state's emissions guidelines. There is information on emissions standards for every state online. Contact your local Department of Motor Vehicle's or an emissions testing site for more information.
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Step 3
Make sure your vehicle is running properly. If there are any major engine, exhaust problems or other issues, have them fixed before the test. Exhaust leaks will cause you to automatically fail your test. Take your vehicle to a mechanic and explain that you are preparing for an OBD II emissions test. Ask the pro to check for anything that could cause you to fail.
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Step 4
Invest in an OBD II manual. It contains information for emissions testing. AES (see References below) offers am OBD II emission testing guide book on its website.
