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CARB's Clean Truck Check regulation requires most diesel vehicles over 14,000 lbs GVWR in California to be tested twice a year: Within the 90 days before DMV registration is due, and again 6 months later (or 6 months prior for July to December 2025).
Resources
Testing Deadlines
Tests can be submitted up to 90 days in advance.
It's good to do this early in case repair or re-testing is needed.
| CA-registered: If Registration is due in | Non-CA & DMV Exempt: If VIN ends in | Next test deadline is | 90-day test window begins |
|---|---|---|---|
| January or July | 3 or 9 | July | May |
| February or August | 4 | August | June |
| March or September | 5 | March | PAST DUE |
| April or October | 0 or 6 | April | open |
| May or November | 1 or 7 | May | open |
| June or December | 2 or 8 | June | open |
Testing Intervals
| Vehicle type | Tests per year | Every |
|---|---|---|
| Trucks, buses, and most others over 14,000 lbs GVWR | 2 | 6 months |
| Motorhomes: CA-registered and only for recreational, non-commercial, or emergency use | 1 | 12 months |
| Agricultural 🔗 | 1 | 12 months |
Required Test Types
| Fuel | Engine Model Year | Test Type |
|---|---|---|
| Diesel | 2013 & later | OBD (most common) |
| Diesel | pre-2013 | OVI / SAE J1667 smoke opacity test & visual inspection |
| Alternative (CNG, LNG, LPG, biodiesel, etc.) | 2018 & later | OBD |
| Alternative | pre-2018 | Visual inspection only |
This information is provided for convenience. Check the CARB portal 🔗 for your own vehicle requirements.
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Frequently Asked Questions
Which vehicles are subject to Clean Truck Check testing?
â–¸ Generally, non-gasoline vehicles with GVWR over 14,000 lbs. This inludes diesel, diesel hybrids, alternative fuel (e.g., natural gas) and alternative fuel hybrids. When are Clean Truck Check tests required?
▸ Generally, tests are due twice a year: Before the vehicle's CA DMV registration date, and again 6 months from the registration date. CA-registered motor homes and agricultural vehicles only need to be tested once per year. See our Resources for details.Tests can be submitted no more than 90 days before the deadline. It's good to get tested at least a month before your due date in case any repairs are needed to pass.See our Deadlines table for details. There are some exceptions and nuances, so be sure to check your own deadline in the CARB portal 🔗. Do I need to register my vehicles with CARB, or pay any fees?
▸ Yes, CARB has a portal for vehicle owners 🔗 to register and pay the $31.18 per vehicle annual fee 🔗. (This is paid directly to CARB and is not part of your DMV registration.) If you haven't yet created your CARB CTC-VIS account and registered your vehicles in the program, this video explains it in detail: Clean Truck Check Reporting Tutorial - YouTube What is CARB?
▸ The California Air Resources Board 🔗, the state agency who administers the Clean Truck Check 🔗 (aka HD I/M) program. Do vehicles registered outside of California need to comply?
▸ Yes, most out-of-state non-gasoline vehicles over 14,000 lbs GVWR that operate in California are subject to the Clean Truck Check registration and test requirements. A vehicle can get only one five-day exemption pass 🔗 per year. Out-of-state motor homes are exempt from the program. What is an "OBD" test?
â–¸ It's On-Board Diagnostics. It allows our test equipment to check the status of your vehicle's emissions system and send the results to CARB. OBD has been required on new vehicles for many years. The check engine light is on, or was on recently. Is that OK?
â–¸ No. A check engine/malfunction indicator light on the dash will cause the test to fail. After you get the problem fixed and the indicator light cleared, the vehicle needs to be driven before testing. Try to complete 5 warm-up cycles of at least 40-50+ miles, with a cool-down of at least an hour. For pre-2013 diesel engines, can you also do smoke opacity tests?
â–¸ Yes, we have testers in our network who perform the more extensive OVI / SAE J1667 smoke opacity testing and visual inspection. Can you test our trucks at a job site?
Yes. Can we get a fleet discount?
â–¸ Yes. The testers in our network will work with you on fleet pricing and scheduling.
Need a test?
To connect with a tester in your area, or for any questions:
About us
CleanTruck.net is a network of CLEAN TRUCK CHECK testers credentialed by the State of California Air Resources Board. Our network members operate independently.