What happens in those 30 minutes
Which checks your car gets depends on its model year. BAR lists the parts of the inspection on its Smog Check page:
| Check | What the inspector does | Which vehicles |
|---|---|---|
| Visual inspection | Looks for missing, modified or disconnected emissions parts | All |
| Functional inspection | Tests that emissions parts work, including the check engine light | All |
| On-board diagnostic check | Plugs into the car's computer to read trouble codes and readiness monitors | Most 2000 and newer |
| Tailpipe emissions test | Measures exhaust gases with a probe | Pre-2000 model years |
Before the inspection starts, the station must give you a written estimate and you must approve it. On a pass, the station charges the $8.25 state certificate fee.
What makes a smog check take longer
- A wait for a free bay. The 30 minutes starts when your car goes in. Some stations take appointments; you can find one near you and check its hours first.
- Readiness monitors that haven’t run. After a dead battery, a battery swap or cleared codes, the car’s self-tests start over. BAR suggests driving for a week or two before the test. Since October 1, 2025, BAR’s rules say all monitors that can feasibly be set must be complete to pass, phased in by vehicle as BAR collects data (BAR, Fall 2025).
- A check engine light. A vehicle will not pass with it on, so fix the cause first (check engine light and smog checks).
- A failure. The car has to be repaired and inspected again, which can take days. Read what to do after a failed smog check and whether you qualify for state repair assistance.
How long a smog certificate is good for
A passing certificate is valid for 90 days and goes to the DMV electronically, so there is no paper to mail (BAR). Plan the test inside the 90 days before you renew or sell. If you are selling, the certificate is yours to provide: the DMV says the seller must give the buyer a valid smog certification.
How often California requires a smog check
| Situation | Smog check needed? |
|---|---|
| Registration renewal | Every other year, once a gasoline or hybrid vehicle is more than eight model years old; every other year for a 1998-or-newer diesel, with no new-vehicle exception |
| Renewal, gasoline or hybrid vehicle eight model years old or newer | No. A yearly smog abatement fee is paid instead |
| Change of ownership | Yes, unless a gasoline or hybrid vehicle is four model years old or newer (the buyer pays an $8 smog transfer fee instead). Diesels always need one |
| Registering in California for the first time | Yes |
| Transfer between immediate family members | No |
Most of California requires the renewal smog check; a few areas only require one at a change of ownership. Your DMV renewal notice says whether this year’s renewal needs one. The full list of who needs one and who is exempt is in smog check requirements.
Frequently asked questions
Ninety days. A passing result is sent to the DMV electronically and stays valid for 90 days, so the registration renewal or the sale has to go through within 90 days of the pass.
Every other year at registration renewal, once a gasoline or hybrid vehicle is more than eight model years old (1998-and-newer diesels have no new-vehicle exception). A smog check is also required when a vehicle changes owners, unless it is a gasoline or hybrid vehicle four model years old or newer, and when a vehicle is registered in California for the first time.
A drive cycle is the mix of driving (a cold start, steady highway speed, idling, slowing down) that lets the car’s computer run its emissions self-tests, called readiness monitors. Disconnecting the battery or clearing trouble codes resets those monitors, and the car can’t pass until they have run again. BAR suggests driving normally for a week or two before the test.
Yes, as long as you renew within 90 days of passing. If the renewal is more than 90 days away, wait: the certificate would expire first.
Right away. The station sends the result to the DMV electronically when the inspection finishes. BAR's public inspection history updates once a day, at midnight.