California’s Clean Truck Check Program Expansion: Your Essential Guide to New 2024 Testing Requirements for Medium-Duty Vehicles
California’s Clean Truck Check program has officially entered its most comprehensive phase yet, with emissions compliance testing requirements effective starting on October 1, 2024. This expansion marks a critical milestone for operators of medium and heavy-duty vehicles throughout the state, fundamentally changing how commercial trucking maintains regulatory compliance.
Understanding the New Testing Requirements
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 and highways even if they are not registered in California. The program encompasses public vehicles (federal, state, and local government); motorcoaches; transit, shuttle and school buses; hybrid vehicles; commercial vehicles; personal vehicles; California registered motorhomes; single vehicle fleets; and vehicles registered outside of California (not including motorhomes).
The testing schedule has evolved significantly since the program’s inception. All compliance deadlines on or after January 1, 2025 will require the submission of a passing emissions compliance test as part of the vehicle’s compliance demonstration. For most vehicles, semi-annual passing test submission are required, meaning twice-yearly testing becomes mandatory.
Key Changes for 2024 and Beyond
The program implements a phased approach to testing frequency. In 2024, there is only one test required per vehicle as testing deadlines will begin no sooner than July 2024. Testing deadlines are based on your DMV registration or the last digit of the VIN (for non-California registered vehicles and vehicles exempt from California DMV registration) In 2025 and 2026, there will be semi-annual testing for non-agricultural vehicles and non-California registered motorhomes.
Looking ahead, beginning October 2027, on-board diagnostics (OBD) equipped vehicles will be required to undergo testing four times per year ONLY for vehicles equipped with On-Board Diagnostic Systems (OBD). This represents a significant increase in testing frequency for newer vehicles equipped with advanced diagnostic systems.
Testing Technology and Procedures
The Clean Truck Check program utilizes sophisticated diagnostic technology. CARB cites the most common protocols for Heavy-Duty/Medium-Duty vehicles are SAE J1939 and J1979. In general, vehicles with Ford/Hino/Isuzu/Volvo engines are using the SAE J1979 (or OBD II) connector, and vehicles with Cummins/ Detroit Diesel/Navistar/Paccar engines are using the SAE J1939 connector.
OBD-equipped vehicles are required to undergo a scan of the engines’ OBD data using a CARB-validated OBD test device. Non-OBD vehicles are required to undergo a smoke opacity test and a visual inspection of the vehicle’s emissions control equipment, referred to in this program as the Vehicle Emissions Control Equipment Inspection.
Compliance Costs and Deadlines
Vehicle owners face both testing and administrative costs. For example, the compliance fee for 2025 will be $31.18, representing an annual fee that increases in accordance with California’s Consumer Price Index. Emissions compliance testing must be performed by a CARB credentialed tester and passing tests may be submitted by the tester up to 90 days prior to the vehicle’s compliance deadline to allow time for any necessary repairs.
The consequences of non-compliance are severe. Non-compliance may result in DMV registration blocks and other enforcement action. Additionally, registration holds are being placed by the California Department of Motor Vehicles (DMV) on vehicles that do not comply with Clean Truck Check requirements, including those with CA DMV-exempt license plates.
Professional Testing Services: All Smog Motors
For vehicle operators seeking reliable compliance solutions, professional testing services have become essential. All Smog Motors Clean Truck Check provides comprehensive mobile testing services throughout Los Angeles and Riverside Counties. All SMOG Motors is CARB-credentialed, uses certified OBD equipment, and comes to your yard. Our service area covers both Los Angeles and Riverside Counties, which means operators running freight along the I-215 corridor through Perris, staging near Ramona Expressway, or hauling out of the distribution centers off SR-74 are squarely in our coverage zone.
The mobile service model addresses a critical need for busy commercial operators. You don’t bring your truck to us. We come to wherever your truck is your yard, your dock, your staging area off Ramona Expressway, wherever it lives between runs. For operators in Perris who are running loaded semis on tight dispatch schedules, that matters.
The Testing Process
Modern Clean Truck Check testing has been streamlined for efficiency. When our tester arrives, we connect a CARB-certified OBD device directly to your truck’s diagnostic port. The system reads your emissions data in real time no smoke test, no visual inspection theater. It’s a direct read of what your engine management system is actually reporting.
For fleet operators, scheduling multiple trucks in a single visit is far more efficient than sending them out one at a time to a fixed location. When you book for a fleet, the process is the same for each truck CARB-certified OBD device connected to the diagnostic port, real-time emissions read, direct electronic submission to CTC-VIS for each passing vehicle. The difference is that it’s done on-site, on your schedule, with minimal disruption to dispatch.
Preparing for Future Requirements
With the regulatory landscape continuing to evolve, proactive compliance planning becomes crucial. With the 2027 quarterly testing mandate on the horizon which will require four tests per year per qualifying truck establishing a fleet testing routine now makes the transition significantly smoother.
The Clean Truck Check program represents California’s commitment to reducing emissions from the transportation sector. When fully implemented, the regulation is projected to cut statewide NOx emissions by over 81 tons per day and PM emissions by 0.7 tons per day in 2037. Together, these emissions reductions will result in over 7,500 avoided premature deaths.
For commercial vehicle operators, staying ahead of these requirements isn’t just about regulatory compliance—it’s about maintaining operational continuity in California’s increasingly regulated transportation environment. Professional testing services, proper scheduling, and understanding the technical requirements ensure that your fleet remains compliant and operational as these new standards take full effect.