What Is California's Clean Truck Check? Complete Guide

The program at a glance

Clean Truck Check replaced California's long-running Periodic Smoke Inspection Program (PSIP) on October 1, 2024. Where PSIP was a once-yearly visual smoke check, Clean Truck Check ties on-highway operation in California to three running requirements that every covered vehicle has to maintain:

The vehicle is registered in CTC-VIS (CARB's online vehicle inspection system).
The annual $30-per-vehicle compliance fee is paid.
A passing emissions test is completed for the current compliance window.

Miss any one of those and the vehicle is flagged non-compliant — which means DMV registration holds, denied entry at ports and railyards, and exposure to per-day enforcement penalties.

Who must comply

Clean Truck Check applies to almost every diesel and alternative-fuel heavy-duty vehicle with a Gross Vehicle Weight Rating (GVWR) over 14,000 lb that operates on California public roads. "Alternative fuel" means natural gas, propane, ethanol, methanol, or any non-diesel/non-gasoline blend — it does not include electric or hydrogen vehicles.

Specifically covered:

Commercial trucks and tractors
Motorcoaches and transit buses
Hybrid heavy-duty vehicles
Public-fleet vehicles (federal, state, and local government)
California-registered motorhomes
Out-of-state and out-of-country vehicles entering California

The out-of-state coverage is worth emphasizing: registration location doesn't exempt a truck from the rule. A Canada-registered tractor pulling into the Port of Long Beach is subject to Clean Truck Check exactly the same as a California-registered tractor.

The $30 annual compliance fee

Every covered vehicle pays an annual compliance fee, currently set at $30 per vehicle per year. The fee adjusts annually with the California Consumer Price Index, so plan for modest year-over-year changes. The fee is paid through CTC-VIS by debit card, credit card, or eCheck.

Processing times to keep in mind:

Credit and debit card payments clear in 1–2 business days.
eCheck payments can take up to 7 business days.
After payment posts, the compliance certificate is downloadable from the "Vehicles" section of CTC-VIS.

Federal-government vehicles are currently exempt from the annual fee, although CARB has signaled future rulemaking may change that.

Emissions testing

On top of the annual fee, every covered vehicle has to submit passing emissions tests on a schedule. The testing requirement went live October 1, 2024, with the first compliance deadlines falling in January 2025.

Testing frequency

2024 through 2027: Most vehicles test 2× per year.
Starting October 2027: OBD-equipped vehicles move to 4× per year (one test per quarter), to support every compliance deadline that falls in 2028 and later. The first quarterly cadence kicks off in Q4 2027 because the testing window opens 90 days before the deadline.
Non-commercial motorhomes and agricultural vehicles stay on an annual cadence even after the quarterly shift.

OBD vs. non-OBD testing

Whether your truck does OBD or non-OBD testing depends on engine model year and fuel type:

OBD testing: diesel vehicles with 2013-or-newer engines, or alternative-fuel vehicles with 2018-or-newer engines. A CARB-certified OBD device reads the truck's on-board diagnostics and submits the result to CARB.
Non-OBD testing: older vehicles below those cutoffs. Requires smoke-opacity testing (SAE J1667-compatible smoke meter) plus a visual emissions equipment inspection.

Three ways to actually get the test done

CARB lets you satisfy a Clean Truck Check test three different ways, and any one of them works for compliance:

In-shop testing at a credentialed tester's location. Browse local options on the directory.
Mobile testing where a credentialed tester comes to your yard. Common in Southern California — see Clean Truck Check Pro.
Clean Truck Check device subscription — a CARB-certified device installed in the truck submits results automatically. See Smart CTC.

We have a more detailed side-by-side comparison covering cost, downtime, and the situations where each option wins.

How compliance deadlines are set

Each vehicle gets a fixed compliance deadline that doesn't move, even if DMV registration dates shift later. How it's determined:

California-registered vehicles: the DMV registration expiration date.
Out-of-state vehicles: the last digit of the VIN maps to a fixed month.
SE-plate vehicles: follow the DMV registration expiration.
DMV-exempt government vehicles: follow the last digit of the VIN.

The testing window opens 90 days before the deadline, so a vehicle with a January 1 deadline can submit its test any time from October 3 of the prior year through the deadline. Not sure when your next test is due? Use the test deadline calculator.

Five-day pass: A vehicle operating in California for a short trip can request one 5-consecutive-day pass per calendar year — useful for one-off cross-border runs. The request has to go in 7 business days before entering the state.

Exempt vehicles

The following are not subject to Clean Truck Check:

Zero-emission vehicles (electric, hydrogen)
Military tactical vehicles
Emergency vehicles
Historical vehicles authorized under California Vehicle Code §5004
New vehicles whose engines are certified to ≤0.01 g/bhp-hr NOx (2023–2027 model years only)
Motorhomes registered outside California
Vehicles operating under experimental permit

Note: there is no low-use exemption. A heavy-duty truck that runs in California even one day per year is still required to register in CTC-VIS, pay the annual fee, and test on schedule.

Enforcement and penalties

CARB enforces Clean Truck Check on the road and at the borders, backed by California Highway Patrol. Inspections happen at port entrances, railyards, weigh stations, and through Remote Emissions Monitoring Devices and Automated License Plate Readers (ALPR) stationed across the freight network.

What that looks like in practice:

Non-compliant vehicles can be denied entry to ports and railyards in real time.
CARB transmits the compliant-VIN list to DMV nightly; non-compliance triggers a DMV registration hold.
A flagged vehicle gets a Notice to Submit to Testing (NST) and has 30 calendar days to provide a passing test. Missing that window carries penalties of $1,000–$10,000 per day, per vehicle.
Operating an uncertified, tampered, or illegally-modified vehicle is a separate violation with fines up to $37,500 per violationunder CA Health & Safety Code §§43016, 43154.

Frequently asked questions

What is California's Clean Truck Check?

Clean Truck Check is California's Heavy-Duty Inspection and Maintenance (HD I/M) program. It's a statewide emissions program administered by the California Air Resources Board (CARB) that requires nearly all diesel and alternative-fuel heavy-duty vehicles over 14,000 lb GVWR to register, pay an annual fee, and pass periodic emissions tests in order to legally operate on California public roads.

Which vehicles must comply with Clean Truck Check?

Almost every diesel or alternative-fuel heavy-duty vehicle with a Gross Vehicle Weight Rating over 14,000 lb that operates on California roads — regardless of where the vehicle is registered. That includes commercial trucks, motorcoaches and transit buses, hybrid trucks, federal/state/local government vehicles, California-registered motorhomes, and out-of-state vehicles entering California. Zero-emission vehicles, military tactical vehicles, emergency vehicles, historical vehicles, and out-of-state motorhomes are exempt.

How much does Clean Truck Check cost?

The annual compliance fee is currently $30 per vehicle, adjusted annually with the California Consumer Price Index. That's separate from the cost of each emissions test, which is paid to a CARB-credentialed tester. Federal-government vehicles are currently exempt from the fee.

How often do trucks need to be tested?

From 2024 through 2027, most vehicles test twice per year. Starting October 2027, OBD-equipped vehicles test four times per year (one test per quarter); non-commercial motorhomes and agricultural vehicles stay on an annual cadence.

Who is allowed to do the test?

Only a CARB-credentialed tester using a CARB-certified testing device can submit a valid Clean Truck Check test. Browse the CTC Directory for credentialed testers in your area, or use a Clean Truck Check device subscription (like Smart CTC) to test remotely without a shop visit.

What happens if a truck fails or doesn't comply?

Non-compliant vehicles can be denied entry to ports and railyards, may have DMV registration holds applied, and can be flagged by Remote Emissions Monitoring Devices (REMD) or Automated License Plate Readers (ALPR) on the road. Failing to address a Notice to Submit to Testing within 30 days carries penalties of $1,000–$10,000 per day per vehicle. Operating an uncertified or tampered vehicle is a violation carrying fines up to $37,500 per violation.

What's CTC-VIS?

CTC-VIS (Clean Truck Check Vehicle Inspection System) is the online portal at cleantruckcheck.arb.ca.gov where vehicle owners register their fleet, pay the annual fee, download compliance certificates, and view test status. Every vehicle subject to Clean Truck Check must be reported in CTC-VIS.

Find a CARB-credentialed tester

The CTC Directory lists every active CARB-credentialed Clean Truck Check tester in the United States, plus Smart CTC's Clean Truck Check device for fleets that prefer remote testing.

Browse California testers All states

Editorial summary by the CTC Directory team. Source: CARB Clean Truck Check FAQ. Regulations and program details change — verify specific requirements directly with CARB before relying on any of this for a compliance decision.