What Matt's Smog Tests
Matt's Smog is a chain of California emissions testing stations. They test whether your vehicle meets the state's emissions standards — specifically, they measure tailpipe output for nitrogen oxides, particulate matter, and other pollutants that vary by your vehicle's model year and engine type. The test itself takes about 10 to 15 minutes and costs between $30 and $50, depending on your vehicle class and whether you need a pre-inspection.
The test result is either a pass or a fail. If you pass, you receive a certificate that you take to the DMV or print and keep with your registration. If you fail, Matt's Smog provides a written report showing which emissions standards your vehicle did not meet. You then have the option to repair the vehicle and retest, or in some cases, pursue a referee inspection through the state if you believe the test was wrong.
Matt's Smog does not repair vehicles — they only test. If your vehicle fails, you will need to take it to a repair shop, which may be at a different location. Some Matt's Smog locations offer referrals to repair shops, but the repair work itself happens elsewhere.
Key Takeaways
- Matt's Smog measures tailpipe emissions to confirm your vehicle meets California standards; the test takes 10 to 15 minutes and costs $30 to $50.
- A passing test gives you a certificate to present at the DMV; a failing test provides a report showing which emissions standards your vehicle did not meet.
- Matt's Smog only tests vehicles — they do not perform repairs, so you will need to find a separate repair shop if your vehicle fails.
- Bring your vehicle registration, proof of ownership, and a valid ID; some locations may ask for your vehicle's VIN before you arrive.
- If you believe the test result is incorrect, you can request a referee inspection through the California Department of Consumer Affairs.
What Documents to Bring to Your Test
Bring your vehicle registration, proof of ownership (such as your title or loan documents), and a valid photo ID. Matt's Smog will use your registration to pull your vehicle's history and confirm that you are the registered owner or an authorized driver. Some locations ask you to provide your vehicle identification number (VIN) when you call or book online, so they can pre-load your vehicle's information and speed up the check-in process.
If your vehicle is registered in another state or you are testing a vehicle that is not yet registered in California, call the Matt's Smog location ahead of time to confirm what documents they will accept. Some locations have different procedures for out-of-state vehicles or vehicles with pending registration.
How the Test Works and What Happens Next
When you arrive, a technician will visually inspect your vehicle for obvious emissions equipment problems — things like a missing gas cap, a disconnected hose, or a check engine light that is on. If the vehicle passes the visual inspection, the technician will connect a probe to your tailpipe and run the emissions test. The probe measures the concentration of pollutants in your exhaust over a set cycle.
The test results print when ready. If you pass, you receive a certificate with a unique number. You take this certificate to the DMV when you renew your registration, or you can print it if the test was done electronically. If you fail, the report will list the specific emissions standards you did not meet and the measured values compared to the legal limits. The report also notes whether the failure is due to a malfunction or a design issue with your vehicle.
You typically have 30 days from the test date to repair your vehicle and retest at no additional charge if you return to the same Matt's Smog location. Some locations offer a one-time free retest; confirm this when you receive your failing report.
What to Do If Your Vehicle Fails
A failing emissions test means your vehicle's tailpipe output exceeds California's limits for one or more pollutants. The report will specify which standard was not met — for example, "NOx exceeds limit" or "PM exceeds limit." This usually points to a specific system that needs repair: a faulty oxygen sensor, a clogged catalytic converter, a fuel injector problem, or an issue with the engine control computer.
Take the failing report to a repair shop. The report gives the repair technician a starting point, though they will still need to diagnose the exact cause. Repairs can range from $50 to $500 or more, depending on what is broken. After repair, you return to Matt's Smog (or another testing station) to retest. If you retest at the same location within 30 days, many locations waive the retest fee.
If you believe the test result is incorrect — for example, if your vehicle passed at another testing station — you can request a referee inspection. Contact the California Department of Consumer Affairs, Bureau of Automotive Repair, to find a referee station in your area. A referee inspection costs more than a standard test but is binding if you disagree with the original result.
Preparing Your Vehicle Before Testing
Before you go to Matt's Smog, check that your gas cap is tight and present. A loose or missing gas cap is one of the most common reasons for a failed visual inspection and can trigger a check engine light. Make sure your check engine light is off; if it is on, the vehicle will fail the visual inspection and you will not be able to test until you address the underlying problem.
Warm up your vehicle before you arrive. Drive it for at least 10 to 15 minutes so the engine reaches normal operating temperature. A cold engine can produce higher emissions readings and may cause a false fail. Do not rev the engine or drive aggressively on the way to the test — just normal driving is enough to warm it up.
If your vehicle has been sitting unused for more than a few weeks, consider taking it for a longer drive a day or two before the test. This helps clear out any buildup in the fuel system and gives you a chance to notice if there are any obvious problems before you arrive at the testing station.
Finding a Matt's Smog Location Near You
Matt's Smog has multiple locations across California. You can find the nearest one by visiting their website or calling their main line; most locations accept walk-ins, but some accept appointments only. Call ahead to confirm hours and whether you need to book in advance, especially during peak times like the end of the month when many people are renewing registrations.
When you call, ask about the test fee for your vehicle type (motorcycle, car, truck, or commercial vehicle all have different rates) and whether they offer a free retest if you fail. Some locations also offer smog check services for vehicles that are exempt from testing — for example, if you are selling a vehicle and the buyer wants proof of emissions compliance — so confirm that your vehicle needs a standard smog test.
Frequently Asked Questions
Can I test my vehicle at any smog check station, or does it have to be Matt's Smog?
You can test at any California-licensed smog check station, not just Matt's Smog. The test result is the same regardless of which station you use. Matt's Smog is one option, but you may also find independent stations or stations run by repair shops. The certificate is valid at the DMV no matter where you tested.
What if my vehicle is too old or too new to test?
Vehicles model year 1975 and older, and some newer vehicles (typically 2024 and newer, depending on state rules), are exempt from smog testing. Vehicles registered in California as model year 1976 and newer generally require testing. Call Matt's Smog with your vehicle's year, make, and model to confirm whether your vehicle needs to be tested.
How long is a smog certificate good for?
A passing smog certificate is good for 60 days from the test date. You must present it to the DMV or renew your registration within that window. If the certificate expires before you renew, you will need to test again.
What if I fail the test and cannot afford repairs right away?
You have 30 days from the test date to repair and retest. If you cannot repair within that time, you will need to retest at a new station, which means paying the test fee again. Some repair shops offer payment plans or financing for emissions repairs, so ask when you get a repair estimate.
Can I dispute a failing test result?
Yes. If you believe the test was wrong, you can request a referee inspection through the California Department of Consumer Affairs, Bureau of Automotive Repair. A referee station will retest your vehicle, and that result is binding. Referee tests cost more than standard tests but are used when there is a disagreement about the original result.