Diesel Smog Check in California: Which Trucks and Cars Need It
In California, diesel vehicles from model year 1998 and newer with a gross vehicle weight rating (GVWR) of 14,000 lbs or less need a smog check every two years and when sold. Diesels from 1997 and older are exempt. Heavier diesel trucks over 14,000 lbs are covered by the California Air Resources Board (CARB) Clean Truck Check program instead of the regular smog check.
Which diesels need a test
| Diesel vehicle | Program |
|---|---|
| Model year 1997 or older | Exempt |
| 1998 or newer, up to 14,000 lbs GVWR | Regular Smog Check (BAR) |
| Over 14,000 lbs GVWR | Clean Truck Check (CARB) |
What the diesel test includes
A visual inspection of the emissions parts (diesel particulate filter, EGR, catalysts), functional checks, and on newer trucks an on-board diagnostics scan. A lit check engine light or a missing part means a fail.
Price
Stations set their own diesel price, which is often higher than for gasoline cars. The $8.25 state certificate fee applies when the vehicle passes. More on smog check costs.
Find a smog station
- Smog check in San Jose — 2 listings
- Smog check in Anaheim — 1 listing
- Smog check in Los Angeles — 1 listing
- Smog check in Sacramento — 1 listing
- Smog check in San Diego — 1 listing
- Smog check in San Francisco — 1 listing
- Smog check in Santa Clara — 1 listing
- Smog check in Sunnyvale — 1 listing
Frequently asked questions
Where do I find my GVWR?
On the label in the driver-side door jamb. GVWR is the maximum loaded weight, not the empty weight of the truck.
Can any smog station test a diesel?
Not every station is equipped for diesels. Call ahead and ask whether the station tests diesel vehicles and what it charges.
Do diesel trucks with deleted DPF or EGR pass smog?
No. Removing or disabling emissions equipment fails the visual and software checks, and it is illegal to drive on public roads in California.
What happens if my car fails the smog check?
The station gives you a report showing why it failed. Have the car repaired at a licensed smog repair station and retest it. California's Consumer Assistance Program (CAP) can help eligible owners with repair costs or with retiring the vehicle.
Related guides
- Which Cars Are Exempt From the California Smog Check? (2026) — The 8-model-year rule, electric vehicles, motorcycles, pre-1976 cars, diesels and the smog abatement fee: who needs a smog check in California and who does not.
- Failed a Smog Check in California? What to Do Next — Why cars fail the California smog check, how to read the Vehicle Inspection Report, where to get repairs, how retests work and where to get help paying.
- How Much Does a California Smog Check Cost? (2026) — Smog check prices are set by each station, plus a fixed $8.25 state certificate fee. What changes the price, who is exempt and what happens if you fail.