Where to take your vehicle for a smog test in San Francisco
San Francisco does not have its own smog test program. Instead, you take your vehicle to any STAR station (Smog Check Test and Repair) anywhere in California. STAR stations are private repair shops certified by the state to perform smog tests. You do not have to go to a dealership, and you do not have to use a station near your home — any certified station in the state will issue a test result valid statewide.
To find a STAR station, use the California Bureau of Automotive Repair's online locator at bar.ca.gov. Search by zip code or address. The locator shows which stations perform tests only (no repairs) versus stations that do both. If you want a test-only shop to avoid pressure to buy repairs, filter for "test only" stations. Most charge between $30 and $50 for a smog test, though the state does not set a fixed price.
You can also call ahead to confirm the station is open and ask about wait times. Some stations take walk-ins; others require appointments, especially during peak testing periods in the weeks before registration renewal important date.
Key Takeaways
- Any STAR station in California can perform your smog test; you do not need to use one in San Francisco.
- The California Bureau of Automotive Repair's online locator at bar.ca.gov shows certified stations near you and whether they perform tests only or tests plus repairs.
- Smog test costs vary by station but typically range from $30 to $50.
- Your vehicle must pass the test before you can renew your registration, and the test result is valid for 30 days.
- Vehicles older than 1976 and some newer low-emission vehicles are exempt from smog testing in California.
What happens during a smog test
A smog test takes 10 to 15 minutes. The technician will connect your vehicle to a machine that measures tailpipe emissions — primarily nitrogen oxides, carbon monoxide, and hydrocarbons. For most vehicles, the test is non-invasive; the probe goes into your tailpipe while the engine runs at idle and at a higher speed. The machine prints a report showing whether your emissions fall within state limits.
Your vehicle must be in running condition to be tested. If the engine will not start or the check engine light is on, the station may refuse to test until you address the problem. Some stations will perform a preliminary scan to check for engine codes before you pay for the full test, so you know whether your vehicle is likely to pass.
If you pass, you receive a certificate valid for 30 days. You take this certificate to the Department of Motor Vehicles (DMV) or renew your registration online if you have a valid smog test result in the system. If you fail, the station will give you a report showing which emissions exceeded limits. You then have 30 days to repair the vehicle and retest at any STAR station.
When your vehicle needs a smog test
In San Francisco, you need a smog test every two years when you renew your vehicle registration, unless your vehicle is exempt. The test must be performed within 30 days before your registration expires. If your registration has already expired, you can still test, but you cannot legally drive the vehicle until you renew.
You also need a smog test if you transfer ownership of a vehicle in California, even if the registration is not due for renewal. The seller or buyer (depending on local rules) must obtain a test before the transfer is complete. Check with the DMV or your local county assessor's office for who is responsible in your situation.
Vehicles from 1975 and earlier are exempt from smog testing. Some newer vehicles — typically those meeting California's Super Ultra Low Emission Vehicle (SULEV) standards — may also be exempt. Check your registration notice or call the DMV to confirm whether your vehicle is exempt before paying for a test.
What to bring to your smog test appointment
Bring your vehicle registration or renewal notice. The technician will need your license plate number and vehicle identification number (VIN) to match the test result to your vehicle. If you have had recent repairs done, bring documentation of those repairs — some stations want to see proof that you addressed a known emissions problem before testing.
Bring a valid form of payment. Most STAR stations accept cash and cards, but call ahead if you want to confirm. You do not need to bring your driver's license, though it is good practice to carry one.
Make sure your vehicle has fuel in the tank. Some stations require at least a quarter tank to perform the test accurately. If your vehicle has a check engine light on, the station will likely scan it before testing; you may want to have that addressed first, or ask the station whether they can test anyway.
What to do if your vehicle fails the smog test
If your vehicle fails, you have 30 days to repair it and retest. The station will give you a detailed report showing which emissions were out of range. Take this report to a repair shop — it does not have to be the same STAR station where you tested. A good repair shop will use the report to diagnose the problem rather than guessing.
Common reasons for failure include a faulty oxygen sensor, a clogged catalytic converter, a bad spark plug, or a fuel system leak. Repair costs vary widely depending on the problem. An oxygen sensor might cost $150 to $300; a catalytic converter can run $800 to $2,000 or more. Before authorizing repairs, ask the shop for an estimate and ask whether they can may provide the vehicle will pass the retest.
After repairs, return to any STAR station for a retest. You do not have to use the same station. The retest fee is the same as the initial test. If you pass the retest within 30 days of the first failure, you can renew your registration. If you fail again, you have another 30 days to repair and retest.
Cost and timing for smog testing
A smog test itself costs $30 to $50 at most STAR stations in the San Francisco area. The state does not set a maximum price, so costs vary. Some stations charge less if you test only; others charge the same whether you test or test and repair. Call a few stations to compare prices if cost is a concern.
The test itself takes 10 to 15 minutes, but wait times depend on how busy the station is. During the weeks before registration renewal important date (typically the end of each month), stations can have long waits. If you schedule an appointment, you can avoid waiting. Walk-in times are usually shorter in the middle of the month.
Plan to test at least 30 days before your registration expires. This gives you time to retest if you fail. If your registration has already expired, you cannot legally drive the vehicle, so testing becomes urgent — but the test itself is still the same price and process.
Frequently Asked Questions
Can I test my vehicle at a station outside San Francisco?
Yes. Any STAR station in California will perform a smog test valid for registration renewal in San Francisco. You do not need to use a station in the city or county. The test result is statewide and valid for 30 days from the test date.
What if I just bought a used car and do not know if it will pass?
Ask the seller for the vehicle's smog test history or maintenance records. If the vehicle recently passed, you may have time before the next test is due. If you are unsure, you can pay for a test yourself before completing the purchase, or negotiate with the seller to provide a passing test as part of the sale. Some used car dealers include a smog test in the sale price.
Do I need an appointment or can I just walk in?
It depends on the station. Use the California Bureau of Automotive Repair locator to find stations near you, then call to ask whether they take walk-ins or require appointments. Appointments are often faster, especially during busy periods near registration renewal important date.
What if my vehicle has a check engine light on?
Most STAR stations will not test a vehicle with an active check engine light. The light indicates an engine fault that could affect emissions. Have the vehicle scanned and the problem diagnosed before testing. Some repair shops will do a free scan; others charge $50 to $100. Fixing the underlying problem is usually necessary to pass the test anyway.
How long is a smog test result valid?
A smog test result is valid for 30 days from the test date. You must renew your registration within that 30-day window. If your registration expires before you test, you cannot legally drive the vehicle, so plan to test well before your renewal important date.