Clean Truck Check is a comprehensive program to ensure the environmental integrity of California's heavy-duty diesel and alternative fuel trucks and buses. Here's a breakdown of the key components and requirements of the program:

EMISSION TEST REQUIREMENTS:

Trucks equipped with On Board Diagnostics (OBD) systems must undergo testing conducted by a CARB-credentialed tester using a CARB-certified readout device. Alternatively, testing and reporting data can be submitted using CARB-certified telematic devices without requiring a CARB-credentialed tester.
Older heavy-duty vehicles lacking OBD systems will follow opacity testing requirements with an additional visual testing component.

Testing Frequency:

• OBD-equipped vehicles are tested twice per year initially, increasing to four times per year after three years.
• Non-OBD-equipped vehicles are tested twice per year.
• Agricultural vehicles and California-registered motorhomes undergo testing once per year.

Training Requirements for Testers:

All emissions testing and reporting must be conducted by credentialed testers, who must renew their credentials biennially. Truck owners can also obtain credentials to conduct their own tests. However, a credentialed tester is not mandatory when using CARB-certified telematics devices for testing and reporting.

Notice to Submit Testing (NST):

Since January 2023, roadside emissions monitoring devices have been deployed across California to identify high-emitting vehicles. Owners of vehicles flagged as potential high emitters receive NST letters and must submit a passing emissions test to CARB within 30 days. Failure to comply leads to violations, loss of compliance certification, and DMV registration holds.