"Clean Truck Check Credentialed Tester" logo with stylized check mark design.
Two semi-trucks driving on a highway at sunset with the Clean Truck Check logo in the sky.

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Yellow school bus with hood open for maintenance, showing engine components. School bus doors are open, with orange traffic cones placed nearby. Background includes palm trees and a clear blue sky.
White utility truck with equipment in a parking lot near a building.

 Now performing Clean Truck Check inspections

2013 or newer diesel engines

2018 or newer alternative fuel engines

2017 and older alternative fuel engines

  • Heavy-Duty Trucks: GVWR over 14,000 lbs

  • Bus Fleets: All public and private buses, including school and transit buses.

  • Vocational Vehicles: Trucks used for construction, delivery, and specialized tasks.

  • Light-Duty Trucks: Some light-duty vehicles may need inspections based on weight.

  • Transport Refrigeration Units: Vehicles with refrigeration systems for perishable goods transport.

  • Hazardous Material Transporters: Vehicles for transporting hazardous materials.

  • Heavy-Duty Vehicles: Heavy-duty vehicles used to imported goods from other states.

  • Fleet Operations: Companies with multiple vehicles.

    Testing Frequency

  • OBD-equipped vehicles: 2 times per year, increasing to 4 times per year after 3 years

  • Non-OBD equipped vehicles: 2 times per year. Diesel vehicles require smoke opacity test and a visual inspection. Alternative fuel vehicles only required to complete the visual inspection.

  • Agricultural vehicles and California registered motorhomes: Once per year.

    Which vehicles are not subject to the regulation?

The heavy-duty vehicle types shown below are not subject to the regulation:

  • Zero-emission vehicles

  • Military tactical vehicles (title 13, CCR, section 1905)

  • Emergency vehicles (California Vehicle Code section 165 or California Health and Safety Code section 1797.84)

  • Historical vehicles (authorized by California Vehicle Code section 5004)

  • New vehicles with engines certified to the most stringent optional, NOx standard (less than or equal to 0.01 g/bhp-hr) -Only during the first four years of Clean Truck Check implementation (2023-2027)

  • Motorhomes registered outside of California

  • Vehicles operating under an experimental permit (authorized by California Health and Safety Code section 43014