California's Clean Truck Check program requires most diesel trucks over 14,000 lbs to undergo emissions testing. Here's what you need to know to stay compliant and avoid costly penalties.
Clean Truck Check is California’s Heavy-Duty Inspection and Maintenance program, officially approved by CARB in December 2021. The goal is simple: make sure emissions control systems on heavy-duty vehicles are actually working throughout the vehicle’s life.
If your truck has a gross vehicle weight rating over 14,000 pounds and runs on diesel or alternative fuel (like natural gas, propane, or biodiesel), you’re subject to the program. That includes commercial trucks, buses, RVs, motorhomes, government vehicles, and even out-of-state trucks that operate on California roads. Electric and hydrogen vehicles are exempt, but almost everything else falls under the rule.
This applies whether your truck is registered in California or not. Out-of-state operators face the same requirements the moment they cross into California. The program doesn’t care about low mileage or occasional use either—there’s no exemption for trucks that rarely operate in the state.
The program runs on three main pillars: registration, annual fees, and emissions testing. You start by reporting your vehicle in CARB’s Clean Truck Check Vehicle Inspection System, known as CTC-VIS. This is the online portal where everything happens—registration, fee payments, compliance deadlines, and test result submissions.
Once your truck is registered, you pay an annual compliance fee. For 2025, that fee is $31.18 per vehicle, and it adjusts each year based on California’s Consumer Price Index. You can’t mail a check or pay through other CARB systems—it has to go through CTC-VIS using a credit card, debit card, or eCheck.
The testing piece is where it gets more involved. Starting January 1, 2025, most trucks need to pass emissions tests twice a year. Your compliance deadlines are tied to your DMV registration expiration date if you’re California-registered. If you’re out-of-state or have exempt plates, your deadlines are based on the last digit of your VIN. The system will show your specific due dates once you’re registered.
Here’s a key detail: you can submit a passing test up to 90 days before your deadline. That window gives you time to get repairs done if your truck doesn’t pass on the first try. Missing a deadline, though, triggers automatic consequences—registration holds at the DMV, potential fines, and restrictions on operating in California.
CARB also uses roadside emissions monitoring devices and automated license plate readers to screen for high emitters. If your truck gets flagged, you’ll receive a Notice to Submit to Testing. You then have 30 calendar days to submit a passing test performed by a CARB credentialed tester. Ignore that notice, and you’re looking at enforcement action, penalties, and registration blocks.
The testing frequency is increasing over time. Right now, it’s semi-annual for most vehicles. But starting in October 2027, trucks with onboard diagnostic systems—generally 2013 and newer diesel engines—will need to test four times a year. Agricultural vehicles and California-registered motorhomes stay on an annual schedule, but commercial trucks will feel the squeeze.
Not all trucks get tested the same way. The type of test your vehicle needs depends on the engine model year and fuel type.
If your truck has a 2013 or newer diesel engine, or a 2018 or newer alternative fuel engine, you’re in the OBD category. OBD stands for onboard diagnostics—basically, the truck’s internal computer monitors emissions control systems in real time. The test involves scanning the engine’s OBD data using a CARB-certified device. The tester plugs into your truck’s diagnostic port, pulls the data, and uploads it directly to CARB’s system. It’s quick, usually taking less than 15 minutes if your truck’s monitors are ready.
Here’s where OBD truck testing gets tricky: your truck’s monitors need to be “ready” for the test to count. If you’ve recently cleared codes, disconnected the battery, or jumped the truck, those monitors reset. You’ll need to complete multiple drive cycles—sometimes dozens of warm-up cycles, hundreds of miles, and hours of engine run time—before the system is ready again. If your truck isn’t ready, the test comes back as “Not Ready,” and it won’t meet compliance requirements. You’ll have to keep driving the truck under normal conditions and retest.
Older trucks follow a different path. If your diesel engine is 2012 or older, you’re required to complete a smoke opacity test and a visual inspection of emissions control equipment. The opacity test measures how much smoke your truck produces during a snap-acceleration procedure. A technician revs the engine and uses specialized equipment to analyze the exhaust. The visual inspection checks that all emissions components—like diesel particulate filters, catalytic converters, and EGR systems—are present, unmodified, and functioning.
Alternative fuel vehicles with 2017 and older engines only need the visual inspection. They skip the smoke test entirely.
Some heavy-duty vehicles operate with off-road engines even though they’re used on public roads. These trucks are still subject to Clean Truck Check, but since off-road engines don’t have OBD requirements, they default to opacity and visual inspection regardless of model year.
Only CARB credentialed testers can perform these tests. That means the person testing your truck has completed CARB’s free online training course, passed the exam with at least 80%, and holds a valid credential. Those credentials expire every two years and must be renewed. If someone who isn’t credentialed tests your truck, the results won’t be accepted, and you’ll have to test again.
Understanding when your truck needs testing is critical. Miss a deadline, and the consequences hit fast—registration holds, fines, and trucks that can’t legally operate.
For California-registered vehicles, compliance deadlines are based on your DMV registration expiration date. You’ll have a deadline every six months after that date. So if your registration expires in March, you’ll have compliance deadlines in March and September. CTC-VIS tracks these dates automatically once your vehicle is registered.
Out-of-state vehicles and trucks with exempt plates follow a different schedule. Your deadlines are determined by the last digit of your VIN. CARB publishes tables that map VIN digits to specific months, and from there, you have semi-annual deadlines. It’s less intuitive than the registration-based system, so checking your CTC-VIS account regularly is essential.
Failing a Clean Truck Check test isn’t the end of the world, but it does mean you need to act quickly. If your truck fails, you’ll need to get the necessary repairs done and retest before your compliance deadline. The 90-day testing window is designed for exactly this scenario—you can test early, and if you fail, you still have time to fix the problem and submit a passing result.
Repairs can range from simple fixes like replacing a faulty sensor to more involved work on emissions control components. Diesel particulate filters, EGR valves, and catalytic converters are common culprits. Some trucks fail because the check engine light is on, which usually indicates a diagnostic trouble code stored in the system. Other trucks fail the opacity test because of excessive smoke, often caused by poor maintenance, fuel quality issues, or failing injectors.
Once repairs are done, you’ll need to retest with a CARB credentialed tester. If your truck passes, the tester uploads the results to CTC-VIS, and your compliance status updates within a couple of business days. You can then download your compliance certificate from your account.
Missing a deadline is where things get serious. If you don’t submit a passing test by your compliance deadline, your vehicle is automatically flagged as non-compliant. The California DMV places a registration hold on the vehicle, which means you can’t renew your registration until you get compliant. For commercial operators, that’s a truck sitting idle, losing money every day it’s off the road.
CARB enforcement and California Highway Patrol also have the authority to conduct roadside inspections. If your truck is stopped and found non-compliant, you could face citations, out-of-service orders, and fines. Ports and railyards in California are required to verify Clean Truck Check compliance before allowing vehicles to enter. Non-compliant trucks get turned away, which can disrupt delivery schedules and cost you contracts.
The financial penalties are steep. CARB can issue fines up to $10,000 per vehicle per day for non-compliance. Even if you’re not hit with the maximum penalty, the combination of registration holds, missed work, and enforcement costs adds up fast. For fleet operators, multiply that across multiple vehicles, and the impact becomes crippling.
The best approach is to treat your compliance deadlines like registration renewals—non-negotiable dates you plan around. Set reminders 90 days out so you can test early. If your truck fails, you’ll have time to get repairs done without the pressure of a looming deadline. And if you receive a Notice to Submit to Testing from CARB, don’t ignore it. You have 30 days to respond with a passing test, and that clock starts the day the letter is issued.
Getting registered in the CTC-VIS system is the first step to compliance, and it’s something every truck owner needs to do before operating in California. The process isn’t complicated, but it does require accurate information and attention to detail.
You’ll start by creating an account at cleantruckcheck.arb.ca.gov. Use Microsoft Edge if possible—CARB recommends it for the best experience. During registration, you’ll be asked to set up an entity, which is basically your business or ownership account. If you’re an owner-operator with one truck, your entity is just you. If you manage a fleet, you can add multiple vehicles under the same entity and assign location admins or co-admins to help manage compliance.
Once your account is set up, you’ll add your vehicles. You can upload vehicle data in bulk if you have a fleet, or you can enter vehicles individually. You’ll need the VIN, license plate number, and basic vehicle information like make, model, and engine year. If your vehicle is already in CARB’s system from other programs, some of that data may auto-populate. Double-check everything—mistakes in your VIN or plate number can cause compliance issues down the road.
After your vehicles are registered, you’ll see your compliance deadlines and annual fee due dates in the system. The annual compliance fee for 2025 is $31.18 per vehicle. You pay this fee through CTC-VIS using a credit card, debit card, or eCheck. Paper checks are not accepted, and payments made through other CARB portals don’t count toward Clean Truck Check compliance.
The fee is due by your compliance deadline, which is the same date your emissions test is due. Pay it late, and you risk registration holds and penalties. The system processes credit and debit card payments in one to two business days. eChecks can take up to seven business days, so plan accordingly.
Once your fee is paid and your passing test is submitted, CTC-VIS generates a compliance certificate. You can download and print this certificate from the “Vehicles” section of your account. If you’re pulled over by CHP or stopped at a weigh station, you may be asked to show proof of compliance. Having that certificate on hand—either printed or saved digitally—keeps things simple.
If you add or remove vehicles from your fleet, you’re required to update your CTC-VIS account within 30 calendar days. Selling a truck? The buyer is responsible for ensuring compliance within 90 days of the transfer. Buying a used truck? Make sure the previous owner has a passing test on file within that 90-day window, or you’ll be on the hook for testing it yourself right away.
For new vehicles, you have 30 days from the purchase date to register them in CTC-VIS and pay the compliance fee. The first emissions test isn’t due until your first compliance deadline, which gives you time to get familiar with the system.
If you’re managing multiple trucks, the CTC-VIS portal also provides a fleet-wide compliance overview. You can see which vehicles are compliant, which have upcoming deadlines, and which are overdue. That visibility is critical for staying on top of deadlines and avoiding surprises.
