California Air Resources Board

This fact sheet presents information on Clean Truck Check emissions compliance testing requirements, which are effective October 1, 2024, with testing deadlines beginning January 1, 2025. 

Emissions Compliance Testing Requirements 

How often will my vehicle require a passing emissions compliance test? 

Almost all vehicles are subject to semi-annual testing.  Agricultural vehicles (that meet the definition) and California-registered motorhomes for recreational use or emergency occupancy will only be required to undergo testing once per year. 

Beginning October 2027, on-board diagnostics (OBD) equipped vehicles will be required to undergo testing four times per year.  

What are the deadlines for my vehicle’s emissions compliance testing? 

The compliance deadlines will be available in the owner’s Clean Truck Check-Vehicle Inspection System (CTC-VIS) account for each vehicle.
View this video for instructions of where to find your test due dates and results. View Test Details.

Information on annual and semi-annual testing requirements, including how to determine each vehicle’s deadline(s), is available below:

• Clean Truck Check Requirements for Vehicles Subject to Semi-Annual Compliance 
• Agricultural Vehicles & California Motorhomes Annual Compliance Requirements 

Passing Clean Truck Check test results may be submitted up to 90 days before a compliance deadline. Testing deadlines for each vehicle will be shown in your CTC-VIS account and a monthly account summary will be emailed at the beginning of each month listing the number of vehicles with a compliance deadline in the next 90 days and the number of any open enforcement actions.

To see where they are located in your account, visit View Emissions Test Results.

For details and examples, visit Clean Truck Check Requirements for Vehicles Subject to Semi-Annual Compliance.

Agricultural Vehicles & California Motorhomes Annual Requirements 

When can I get my vehicle tested? 

Credentialed testers may submit passing tests up to 90 days prior to the vehicle’s compliance deadline to provide time for any repairs to be made. View Emissions Test Due Dates & Results for instructions on where to find your test due dates and results.

Where can I get my vehicle tested?

Please find Clean Truck Check Credentialed testers at Available for Hire Credentialed Testers.

How must my vehicles be tested? 

The testing requirements depend on whether your vehicle/engine is equipped with OBD or not.

While most vehicles have an engine model year one year older than the vehicle model year, please refer to the vehicles emissions control label (ECL) on the engine to ensure you are performing the correct test for the vehicle. 

OBD-equipped vehicles (2013 and newer diesel engines and 2018 and newer alternative fuel engines) are required to undergo a scan of the engine’s OBD data using a California Air Resources Board (CARB) certified OBD testing device. 

Diesel non-OBD vehicles (2012 and older diesel engines) are required to complete 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. Alternative fuel non-OBD vehicles (2017 and older alternative fuel engines) are only required to complete the visual inspection and are not subject to the smoke opacity test requirement. 

Off-Road Vehicles

Some heavy-duty vehicles (>14,000 lbs. GVWR) that operate on public roads and highways may be equipped with off-road engines. These vehicles are subject to the Clean Truck Check requirements. Currently, there are no OBD requirements for off-road engines, so they are required to complete the Opacity and Visual Inspection regardless of the engine model year.

What are the Non-OBD smoke opacity standards?

Do I need to send/upload my test results to CARB Clean Truck Check?

No, your Clean Truck Check credentialed tester is responsible for sending the results to CARB. You may view your test results in your account. Please visit how to view your test results/due date for more information.

Who can perform emissions compliance testing on my vehicle? 

Emissions compliance testing must be performed by a CARB credentialed tester who has a current Certificate for passing the credentialed tester exam. 

Can I be a credentialed tester? 

Anyone can become a credentialed tester. Visit Credentialed Tester Overview for additional information. 

Where can I find my emissions compliance testing results? 

Vehicle owners can find current and historical emissions compliance testing results in their CTC-VIS account. View Emissions Test Due Dates & Results for instructions of where to find your test due dates and results.

Non-OBD-equipped vehicles will receive either a "pass" or "fail" for emissions compliance testing. In addition to "pass" or "fail", OBD-equipped vehicles may receive other results that require additional testing. 

What are next steps if my vehicle does not pass the emissions compliance test? 

If a vehicle fails the emissions compliance test, the vehicle owner should complete any needed repairs to bring the vehicle back into compliance. The vehicle should be tested post-repair and pass the emissions compliance test before the deadline. 

If an OBD-equipped vehicle receives other types of results, such as "Not Ready", " Vehicle Not Applicable For OBD Testing", and "Invalid Test", the result will not be considered compliant. Please follow the instructions accompanying the test result and retest the vehicle. For example, if an OBD-equipped vehicle receives a "Not Ready" result during the initial emissions compliance testing, the message accompanying the test result will advise the vehicle owner to operate the vehicle further to meet the OBD Readiness Criteria before retesting. Please ensure that the vehicle passes the emissions compliance test before the compliance deadline. 

Other Requirements 

Can my vehicle still be flagged as a potential high emitter even if I passed my last emissions compliance test by the deadline? 

Yes, high-emitter vehicle screening began in January 2023 using roadside emissions monitoring devices. Even if your vehicle passes its emissions compliance test, it still may be identified as a potential high emitter in between testing intervals. If you receive a Notice to Submit to Testing (NST), a passing Clean Truck Check emissions compliance test must be submitted to CARB within 30 calendar days of receipt. Be sure to follow the instructions in the letter you receive from CARB, have the vehicle tested as soon as possible, and have test results submitted to CARB. Once CARB determines your vehicle has a passing emissions test, there is nothing more you will need to do in response to the NST. 

How to get more information about Clean Truck Check 

How can I receive updates on Clean Truck Check activities? 

Subscribe to receive automatic email updates on Clean Truck Check implementation. 

Where do I get additional Clean Truck Check information? 

For more information, visit Clean Truck Check (HD I/M). Fact sheets, videos, and other information on requirements and reporting are available. 

If I have additional questions, how do I contact CARB?

Please contact hdim@arb.ca.gov.