What Is the CARB Clean Truck Check Program? Complete Guide for California Truckers

The CARB Clean Truck Check is California’s mandatory emissions inspection program for heavy-duty diesel and alternative-fuel vehicles over 14,000 pounds GVWR. Officially the Heavy-Duty Inspection and Maintenance (HD I/M) Program, it is run by the California Air Resources Board (CARB) and requires periodic emissions testing to keep your vehicle registration clear.

Fast facts (2026)

• Who it covers: Diesel and alternative-fuel vehicles over 14,000 lbs GVWR operating on California roads.
• Test types: OBD (On-Board Diagnostics) for 2013 and newer diesel engines; OVI (Opacity and Visual Inspection) for 2012 and older engines.
• Testing frequency: Twice per year (semi-annual) through 2026. Beginning October 2027, OBD-equipped vehicles move to quarterly testing (four times per year). Non-commercial motorhomes and agricultural vehicles stay on an annual schedule.
• Annual compliance fee: $32.13 per vehicle in 2026 (up from $31.18 in 2025), paid to CARB separately from any testing fee.
• Miss a deadline: CARB places a hold on your DMV registration until you test and pass.

What is the CARB Clean Truck Check?

The CARB Clean Truck Check, officially called the Heavy-Duty Inspection and Maintenance (HD I/M) Program, is a mandatory periodic emissions compliance program administered by the California Air Resources Board. It requires most heavy-duty diesel and alternative fuel vehicles operating in California to undergo regular emissions inspections to confirm their emissions systems are working within state standards.

The program is part of California’s broader effort to cut particulate matter and nitrogen oxide (NOx) emissions from heavy-duty diesel vehicles.

Who does it apply to?

The Clean Truck Check applies to nearly all diesel and alternative fuel heavy-duty vehicles with a Gross Vehicle Weight Rating (GVWR) over 14,000 pounds that operate on California public roads. That includes commercial trucks, delivery vehicles, buses, motor coaches, privately owned vehicles, and California-registered motorhomes and RVs.

Exemptions include gasoline-powered vehicles, zero-emission vehicles (ZEVs), military tactical vehicles, and most historical vehicles.

How does testing work?

Testing depends on your engine model year.

OBD periodic testing (2013 and newer engines). A CARB-credentialed technician connects a state-approved diagnostic device to your vehicle’s OBD port and reads the emissions system status directly from the vehicle’s computer. Results upload to the CARB portal immediately, so DMV holds typically clear the same business day on a pass.

OVI periodic testing (2012 and older engines). This uses a smoke opacity measurement plus a hands-on visual inspection of the emissions control components. OVI results take several business days to process after submission.

We are credentialed by CARB for both OBD and OVI testing, and we perform both on-site through our mobile on-site testing service.

What happens if you miss a deadline?

If your vehicle misses its compliance testing deadline, CARB notifies the California DMV, which places a hold on your registration renewal. You cannot legally renew registration until testing is completed and results are submitted to CARB. The fastest way to clear a hold is mobile testing that uploads OBD results on the spot. See our guide on clearing a DMV registration hold.

How often is testing required?

Through 2026, subject vehicles test twice per year. Beginning October 2027, OBD-equipped vehicles (2013 and newer diesel engines, 2018 and newer alternative-fuel engines) move to quarterly testing. Non-commercial motorhomes and agricultural vehicles remain annual. Exact deadlines vary by VIN and registration type, and you can look yours up in the CARB Clean Truck Check portal at cleantruckcheck.arb.ca.gov.

How to stay compliant

• Register your vehicle in the CARB Clean Truck Check portal.
• Track your testing deadlines and the 2027 quarterly change if you run OBD-equipped trucks.
• Schedule testing before your deadline, not after a hold lands on your registration.
• Use a CARB-credentialed tester and confirm results are uploaded after each test.

We serve fleets and owner-operators across Sacramento, the Sacramento Region, and the SF Bay Area. Call us at (916) 538-7777 and we can look up your specific schedule.