Annual emissions testing is required in order to ensure that your car is not producing too much pollution and that your emissions control components are in working order. While not all areas of the US require emissions testing yet, those that don’t are becoming rarer. If your car doesn’t pass the emissions test, you’ll be on the hook for repairs and parts replacement required to get it to pass, or you might face fines, fees or other consequences. How do you prepare for an emissions test?
Check Engine Light
First and foremost, if your Check Engine Light is on, your car won’t pass the test. It’s as simple as that. Have the code pulled, and then make the repairs needed. Chances are good it’s something simple, like a damaged spark plug wire, or maybe a damaged gas cap seal or a failed oxygen sensor. Take care of any Check Engine Light related issues before going for your test. You’ll also need to drive the car for a few days after having the Check Engine Light cleared, as part of the test looks at computer history for the vehicle.
One complication that can arise with your test is if your OBD (on-board diagnostics) system is “not ready” for testing. This can happen if the system hasn’t been operated long enough to conduct all of its self-checks. Your car won’t fail, but you’ll be declined and have to retest on another day. The best way around this is to drive your car for at least 20 miles before going to the testing station.
Correct airflow into the engine is critical for emissions, and if your air filter is seriously clogged, it can affect your emissions test results. Change your air filter before the test to make sure that your engine has a steady stream of fresh air for combustion.
Don’t turn off the engine
While you’re waiting for the test at the testing station, keep your engine running. Turn off things like your air conditioner or heater, but leave the engine running with the car in park. This will keep the operating temperature in the normal range (your engine can’t be tested if the exhaust system is too cool).
The best advice is to simply have your car tested, and then make any necessary repairs afterwards. The re-test should be free of charge if done within the window allotted by your state government.
This article originally appeared on YourMechanic.com as How Can I Prepare For an Emissions Test? and was authored by Valerie Johnston.