What is the CARB Clean Truck Check?

The Clean Truck Check is a California Air Resources Board (CARB) program — also known as Heavy-Duty Inspection and Maintenance (HD I/M) — that requires regular emissions testing for heavy-duty trucks and buses operating in California. The goal is to make sure emissions control systems on these vehicles stay properly working throughout the life of the truck.

The program applies to nearly all diesel, alternative fuel, and hybrid vehicles with a Gross Vehicle Weight Rating (GVWR) over 14,000 pounds that operate on California public roads — including vehicles registered outside of California.

Does my vehicle need a Clean Truck Check?

If your vehicle meets all of the following, it is subject to Clean Truck Check requirements:

  • GVWR over 14,000 lbs (most heavy-duty trucks, box trucks, dump trucks, semis, motorcoaches, transit buses, school buses)
  • Diesel, alternative fuel, or hybrid powertrain (gasoline-only vehicles are not subject to the program)
  • Operates on California public roads — even briefly, even if registered out of state

This includes commercial vehicles, government vehicles, and personal-use vehicles. Some agricultural vehicles and California-registered motorhomes have a reduced annual testing schedule rather than semi-annual.

Don't risk a DMV registration hold

The California DMV places registration holds on vehicles that aren't compliant with Clean Truck Check. If your truck isn't tested and reported on time, you may not be able to renew your registration. Penalties can also be issued for operating non-compliant vehicles.

How often does my truck need to be tested?

Most subject vehicles require semi-annual testing — that's twice per year. Compliance deadlines are tied to your DMV registration expiration date and shown in your CTC-VIS (Clean Truck Check Vehicle Information System) account.

Beginning October 2027, OBD-equipped vehicles will be required to test four times per year. Agricultural vehicles and California-registered motorhomes for recreational use remain on an annual testing schedule.

Which test does my truck need?

The required test depends on your engine model year and fuel type:

  • OBD test — for diesel engines model year 2013 and newer, and alternative fuel engines 2018 and newer. We connect to your engine's OBD port using a CARB-certified testing device and scan emissions data.
  • Smoke opacity test + visual inspection — for diesel engines 2012 and older. Includes a tailpipe smoke meter test and a visual inspection of the emissions control equipment.
  • Visual inspection only — for alternative fuel non-OBD vehicles (2017 and older alternative fuel engines). The smoke opacity test does not apply.

Refer to your engine's emissions control label (ECL) to confirm engine model year — it can differ from the vehicle model year.

The Clean Truck Check process

  1. Register the vehicle in CTC-VIS. Each subject vehicle must be reported in the Clean Truck Check Vehicle Information System and have annual compliance fees paid.
  2. Bring the vehicle in for testing. Drive in to 2405 Sycamore Dr — the test takes about 15-20 minutes for most trucks.
  3. We perform the appropriate test based on your engine year and fuel type, using a CARB-certified testing device.
  4. Results are submitted to CARB on your behalf within the 90-day pre-deadline window. Once submitted, your vehicle is compliant.
  5. Keep documentation. Drivers should keep certificates accessible — they may be required at ports, railyards, and roadside checks.

What if my truck fails?

If your vehicle fails the test, you'll receive a detailed report showing the issue. The vehicle will need repairs to bring it back into emissions compliance — usually catalyst, DPF/SCR system, OBD-related sensor, or engine control issues. Once repaired, return for a re-test.

Notice to Submit to Testing (NST)

CARB also uses roadside emissions monitoring devices and license plate readers to flag potential high emitters between regular testing intervals. If your vehicle is flagged, you'll receive a Notice to Submit to Testing (NST) and have 30 calendar days to submit a passing emissions test. We can perform NST testing — bring the notice with you when you come in.

Frequently asked questions

My truck is registered out of state — do I still need a Clean Truck Check?

Yes. Clean Truck Check applies to any subject vehicle that operates on California public roads, regardless of where it's registered. CARB conducts roadside enforcement at border crossings, ports, and railyards.

What's the annual compliance fee?

The fee is set by CARB and adjusted with the California Consumer Price Index each year. Check your CTC-VIS account for the current fee for your vehicle.

Can I do the test myself?

Only CARB-credentialed testers can perform the official test and submit results. Anyone can become credentialed by completing CARB's free online tester course, but you'd still need a CARB-certified testing device.

My vehicle is gasoline-powered. Do I need this?

No. Clean Truck Check only applies to diesel, alternative fuel, and hybrid vehicles over 14,000 lbs GVWR. Gasoline-only vehicles are not subject to the program.

When are my deadlines?

Compliance deadlines are based on DMV registration expiration date and are shown in your CTC-VIS account. Tests can be submitted up to 90 days prior to the deadline to allow time for any repairs.

Ready to get your truck tested?

Drive in to 2405 Sycamore Dr — call ahead for heavy-duty appointments.

Call (805) 526-9716

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