How to prepare for your smog check.
Many failed tests come down to a handful of things you can check before you drive over.
Tip 1: Check engine light on? Fix it first.
If the check engine light is on, your car will not pass. The light means the car’s computer has found a problem, usually in the emissions system.
Have a repair shop read the trouble codes and fix the cause before your test. Some emissions parts and repairs are covered by your vehicle’s warranty, so check that first.
Tip 2: New battery or a jump start? Drive for a week.
Disconnecting or replacing the battery, a jump start, or clearing trouble codes resets the car’s built-in self-tests, called readiness monitors. If they haven’t finished, the car can’t pass yet.
The state recommends driving normally for a week or two before your smog check. Don’t clear codes right before a test.
Tip 3: Modified parts? Make sure they’re approved.
Every smog check includes a look at your emissions equipment. If a part has been removed, disconnected, or replaced with an aftermarket part that isn’t approved by the California Air Resources Board (CARB), the car won’t pass.
Approved aftermarket parts carry a CARB Executive Order (EO) number. If you’ve added performance parts, check for that number, or ask the shop that installed them, before your test.
Tip 4: Running rough? Get it looked at.
If the engine idles rough, hesitates, misfires, smokes, or you can smell fuel, have it checked before the smog test. These problems often cause a fail even when the dashboard looks fine.
Staying current on routine maintenance, including overdue oil changes, keeps the engine running the way it was designed to.
Tip 5: Older car? Check tire pressure.
Most 2000 and newer vehicles are tested through the onboard computer. Many older vehicles get a tailpipe test, which can involve driving the car on a dynamometer (a set of rollers). Tires at the pressure listed on the driver’s door jamb help that test run smoothly.
Tip 6: Bring your DMV renewal notice.
If you have a DMV registration renewal notice, bring it along. It shows whether your vehicle needs a smog check and whether it must go to a STAR station. Your results are sent to the DMV electronically.
Not sure whether your car is ready? Call us at (510) 441-9800. And if it doesn't pass, the retest here is free. For the rules behind the test, see the smog check guide.
Mon-Fri 9:30 AM-5 PM, Sat 9:30 AM-3 PM
Ready for your smog check?
33365 Mission Blvd., Union City.