What is the California Air Resources Board (CARB)?
The California Air Resources Board (CARB) is responsible for regulating air quality and emissions standards to reduce pollution across the state. Its Clean Truck Check (HD I/M Program) is aimed at ensuring heavy-duty diesel vehicles comply with emissions limits to minimize environmental impact.
What is the Clean Truck Check Program?
​The Clean Truck Check (HD I/M) is California’s emissions testing program for diesel-powered vehicles over 14,000 pounds GVWR. The program requires regular emissions testing, registration, and compliance reporting to reduce smog-forming pollutants.
Who Needs to Comply?
All heavy-duty diesel vehicles over 14,000 lbs operating in California must be tested periodically, regardless of where the vehicle is registered.
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Exceptions:
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Zero-emission vehicles
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Military vehicles
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Emergency vehicles
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Historical vehicles,
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Certain new ultra-low NOx engines (2023-2027)
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Out-of-state motorhomes
Testing Frequency
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Semi-Annual Testing (Most Vehicles) – Twice per year testing for most heavy-duty trucks.
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Annual Testing (RVs & Agriculture Vehicles) – Certain vehicles qualify for once-a-year testing.
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Quarterly Testing (Starting in 2027) – Vehicles with 2013+ engines with OBD systems will transition to quarterly emissions checks.
Why It Matters
Non-compliance can result in fines, registration holds, and costly repairs. Staying compliant ensures smooth operations and avoids penalties.
Disclaimer
This page is provided for informational purposes only and is not an official CARB resource. While we strive to keep our content accurate and up to date, regulations, requirements, and deadlines may change.​
For the most current and official information, please visit the California Air Resources Board (CARB) website at: ww2.arb.ca.gov​
If you have specific questions about compliance, we recommend consulting CARB directly or speaking with a certified emissions compliance expert.