CARB Clean Truck Check: Who Must Comply, Tests and Deadlines

Clean Truck Check is CARB’s Heavy-Duty Inspection and Maintenance (HD I/M) regulation, required by Senate Bill 210 (Leyva, Chapter 298, Statutes of 2019). It checks that a heavy-duty vehicle’s emissions control systems, such as diesel particulate filters and selective catalytic reduction, are working.

To be compliant, an owner must report the vehicle in CARB’s Clean Truck Check Vehicle Inspection System (CTC-VIS), pay the vehicle’s annual compliance fee, submit passing emissions tests, and have no outstanding enforcement violations on the vehicle.

Since January 2023, CARB has used roadside emissions monitoring devices to flag vehicles that may be high emitters. A vehicle that receives a Notice to Submit to Testing has 30 calendar days to submit a passing test performed by a CARB credentialed tester.

Sources: CARB, Clean Truck Check - About (posted March 10, 2026) and Compliance Requirements Overview; California Senate Bill 210 (2019). Checked October 1, 2026.

Clean Truck Check applies to nearly all diesel and alternative fuel heavy-duty vehicles with a gross vehicle weight rating over 14,000 pounds that operate on California public roads, including vehicles registered outside California. That covers commercial and personal vehicles, government vehicles, motorcoaches and transit, shuttle and school buses, hybrids, California-registered motorhomes and single-vehicle fleets.

CARB defines alternative fuel as natural gas, propane, ethanol, methanol or another fuel that is neither diesel nor gasoline. Electricity, hydrogen and other zero tailpipe emissions technology are not alternative fuel under the program.

Not subject to the regulation: zero-emission vehicles, military tactical vehicles, emergency vehicles, historical vehicles, motorhomes registered outside California, vehicles operating under an experimental permit, and, during 2023 through 2027 only, new vehicles with engines certified to the optional NOx standard of 0.01 g/bhp-hr or lower.

Source: CARB, Clean Truck Check Compliance Requirements Overview. Checked October 1, 2026.

The test depends on whether the engine has on-board diagnostics (OBD), and that follows the engine’s model year. Go by the engine model year printed on the emission control label on the engine; most engines are one model year older than the vehicle.

Engine	Engine model year	Test
Diesel	2013 and newer	OBD scan with a CARB-certified OBD testing device
Diesel	2012 and older	Smoke opacity test and visual inspection of the emissions control equipment
Alternative fuel	2018 and newer	OBD scan with a CARB-certified OBD testing device
Alternative fuel	2017 and older	Visual inspection only
Off-road engine in an on-road vehicle	Any	Smoke opacity test and visual inspection

A separate CARB rule, the Truck and Bus Regulation, has required since January 1, 2023 that diesel vehicles over 14,000 pounds gross vehicle weight rating operating in California have a 2010 or newer engine and emission system, with few exceptions. The DMV denies registration to vehicles that do not comply.

Sources: CARB, Clean Truck Check Emissions Compliance Testing Requirements; CARB, Truck and Bus Regulation. Checked October 1, 2026.

Emissions testing requirements took effect October 1, 2024, and every compliance deadline on or after January 1, 2025 needs a passing test. Most vehicles must show compliance every six months. Agricultural vehicles and California motorhomes for recreational or emergency use are tested once a year.

A California-registered vehicle’s deadlines fall in its DMV registration expiration month and six months later: a registration expiring in March gives deadlines in March and September. Vehicles registered outside California, and government vehicles with DMV-exempt plates, go by the last digit of the VIN.

Last digit of VIN	Deadline months
0	April and October
1	May and November
2	June and December
3	January and July
4	February and August
5	March and September
6	April and October
7	May and November
8	June and December
9	January and July

A credentialed tester may submit a passing test up to 90 days before a deadline. The annual compliance fee is due at the vehicle’s compliance deadline: $32.13, rising to $33.12 for deadlines on or after January 1, 2027. CARB adjusts it each year by the California Consumer Price Index.

From October 2027, OBD-equipped vehicles move to four tests a year; agricultural vehicles and non-commercial motorhomes stay on one a year. A vehicle out of compliance can have its DMV registration blocked, and most DMV transactions need the vehicle compliant, with no test or fee due within 90 days and no open CARB enforcement action.

Sources: CARB, Requirements for Vehicles Subject to Semi-Annual Periodic Compliance (issued March 13, 2024); Emissions Compliance Testing Requirements; Notice of Update to the 2027 Clean Truck Check Compliance Fee; Vehicle Owner Information. Checked October 1, 2026.

CARB’s Vehicle Compliance Status Lookup shows one vehicle’s Clean Truck Check status from its VIN. It does not cover CARB Five-Day Passes, which are verified by scanning the QR code on the pass itself.

The Entity Compliance Status Lookup checks an owner or company, the Credentialed Testers list finds testers and shows which offer OBD testing, and owners report vehicles and pay fees in CTC-VIS. For the Truck and Bus Regulation, CARB’s Verify Fleet Compliance page checks a fleet.

Sources: CARB, Clean Truck Check Vehicle Inspection System (CTC-VIS); CARB, Truck and Bus Regulation. Checked October 1, 2026.