Smog check tips
Most failed smog tests are avoidable. These simple steps give your vehicle its best chance of passing on the first try.
Before your test
Drive at least fifteen to twenty minutes before your test — some freeway time on I-880 or I-680 is ideal. A warm catalytic converter runs much cleaner.
If the check-engine light is on, an OBD-II vehicle will fail automatically. Have it looked at before your test.
Clearing codes or disconnecting the battery erases the readiness monitors, and the car can’t pass until they reset.
A vehicle serviced on schedule, per the owner’s manual, burns fuel more cleanly and tests better.
Make sure it seals and clicks tight — a worn cap can cause an evaporative-system failure.
Removed or modified emissions parts mean an automatic fail, even if the car runs well.
Readiness monitors
Your vehicle constantly runs self-tests called readiness monitors. After a dead battery, a battery replacement or any work that cleared trouble codes, those monitors reset — and the car can’t pass until enough of them complete again. That usually takes several days of normal mixed driving.
If your vehicle does fail, our resources page explains California’s Consumer Assistance Program, which offers financial help to eligible drivers.
Tips FAQ
At least fifteen to twenty minutes of normal driving, so the engine and catalytic converter are fully warmed up.
Yes. An illuminated check-engine light is an automatic failure for OBD-II vehicles.
Wait a few days. A new battery resets the readiness monitors, and they need several days of driving to complete.
It can. A vehicle serviced on schedule generally runs cleaner on test day.
Yes. A cap that doesn’t seal can trigger an evaporative-system failure.
There’s no shortcut for a healthy engine. Regular servicing and a good warm-up drive matter far more.
Have the issue shown in your test result addressed, drive normally for a few days, then bring it back for a retest.
5505 STEVENSON BLVD. · STAR STATION · TEST-ONLY
(510) 623-1922
