The mission of the Clean Truck Check Referee program, operated by CARBTest.org (also referred to as CARBTest Referee), is to provide independent evaluations of non-gasoline, heavy-duty vehicles with a gross vehicle weight rating (GVWR) over 14,000 lbs.

For questions regarding Clean Truck Check, please email hdim@arb.ca.gov or visit Clean Truck Check program page

Question: How can I speak to a CARBTest Referee directly? 

If you have specific questions that you need to discuss directly with a CARBTest representative, please fill out an online form at https://carbtest.org/contact. Our CARBTest representative will respond to your question via email. 

For more information, please visit https://carbtest.org. 

Question: What are the reasons I would make a CARBTest Referee service appointment? 

CARBTest service appointments will only be available for specific vehicle services detailed in section 2196.7 of the Heavy-Duty Vehicle Inspection and Maintenance Program. Examples include, but are not limited to:  

• You received a CARB Notification requiring your vehicle to have a CARBTest inspection. 

  • Law enforcement agency request 
  • Submitted erroneous OBD testing data or failed to submit required testing data 
  • Notice to Submit to Testing (NST) 
  • Refusal to submit to an inspection 
  • Suspected tampering or defective emission control system. 
  • Unresolved citations 
  • California Highway Patrol (CHP) citations 
  • Auditing or demonstration of compliance purposes 
  • CARB requires the verification of a submitted repair invoice, work order, or other proof of compliance documentation 
  • Other enforcement action 

• Your vehicle’s condition makes it incompatible with CARB Clean Truck Check test procedures due to unusual vehicle configurations, design, or other inspection incompatibility. 

• You would like to dispute an inspection result and request an independent evaluation of a vehicle’s compliance status.  

• You believe your vehicle was improperly tested. 

• You believe your vehicle incorrectly failed the emissions test. 

• You believe your vehicle failed a Clean Truck Check inspection for missing emission control equipment that is not required. 

• You have a dispute over the type of inspection that should be performed (e.g., smoke opacity, visual, OBD). 

• The vehicle engine has been changed. 

• There has been a change to the engine or emission control configuration. For example, 

  • The vehicle has been retrofitted with an alternative fuel system (e.g., natural gas, propane, ethanol, methanol, or other non-diesel or non-gasoline fuel, and includes any of these fuels used in combination with each other and does not include electricity, hydrogen, or other zero tailpipe emissions fuel or technology). 
  • The vehicle has been retrofitted with a gasoline fuel system. 

• You have recently converted your vehicle to a motorhome. 

• You would like to apply for a Parts Unavailability Compliance Time Extension due to the unavailability of the necessary part(s) to repair your vehicle to demonstrate compliance with Clean Truck Check emissions compliance testing requirements. 

• Credentialed Testers are not available for testing your area. 

Question: Is this CARBTest Referee Program the same as the Smog Check Referee Program operated by the Bureau of Automotive Repair? 

No. CARBTest (California Air Resources Board Truck Emission Systems Testing) is specifically part of the California Clean Truck Check Program that is applicable to almost all heavy-duty non-gasoline vehicles operating on California public roads and highways with a gross vehicle weight ratings (GVWR) greater than 14,000 pounds. 

Question: I received a citation for vehicle emissions, and I was told to see CARBTest Referee. Can CARBTest clear the citation? 

CARBTest can ONLY inspect the vehicle to determine if the vehicle passes the required inspection. Once the vehicle has passed the CARBTest inspection, you will need to complete the process of clearing the citation with the issuing agency or court system. Please refer to your citation for this information. 

Question: Can someone else take my vehicle to the appointment? 

Yes. Anyone you choose can bring the vehicle to the appointment if they bring the vehicle and the required paperwork. 

Question: How soon can I find out if my vehicle passed the CARBTest Referee Inspection? 

Upon completion of the inspection, the Referee will provide a Vehicle Inspection Report (VIR) and the CARBTest Referee Tester will review any available results with you. If the vehicle is directed to the Referee Program, the results of the inspection will be either, “Complete” or “Incomplete”, see definitions below. The Vehicle Inspection Report is needed to further process your citation, enforcement action, or CARB verification. In some cases, it may be several days before final results are available. If the vehicle has been directed by the state, we will not be able to provide test results but only that the inspection is complete or incomplete. 

State-Directed testing – Testing required by CARB or law enforcement agency. If you received a notice from California Air Resources Board (CARB) directing your vehicle for CARBTest testing. Examples include, but are not limited to, law enforcement agency request, open CARB enforcement action, Notice to Submit to Testing (NST) letter, unresolved citations, audit purposes, and compliance issues. 

Incomplete (State-Directed Only): If your “State-Directed” inspection is identified as “Incomplete”, you will be required to take the corrective actions listed in the Vehicle Inspection Report (Tampered/Missing/Modified/Etc.). Once the necessary corrective actions have been performed, you must schedule and complete a secondary CARBTest Referee Inspection as directed by CARB Enforcement. 

Complete (State-Directed Only): If your “State-Directed” inspection is identified as “Complete”, you must submit your CARBTest Referee-105 form also known as the “Vehicle Inspection Report” to one of the listed CARB Departments below. The Referee Tester will provide you the Vehicle Inspection Report after your Referee inspection is finished.   

• If you received a citation, you must submit your Vehicle Inspection Report to the Citations Department by email at citations@arb.ca.gov or phone at 916-322-8275. 

• If you received a Notice to Submit to Testing (NST), you must submit your Vehicle Inspection Report to the Enforcement Department by email at HDVehicleEnforcement@arb.ca.gov or phone at 916-229-0492. 

You may still be required to complete additional actions required by CARB Enforcement. Please contact the appropriate CARB department and provide your name, VIN, citation number, and CARBTest Vehicle Inspection Report to obtain additional information. 

Question: Can CARBTest Referee help me make emissions-related repairs? 

No. The CARBTest Referee inspector does NOT make repairs, recommend repairs, or perform diagnostic tests. However, they can help you to understand what issues caused the failure or what emissions systems appear to be not working properly. 

Question: What should I bring to my CARBTest Referee appointment? 

You will be provided with a list of what to bring when you schedule your appointment. Generally, you will be required to bring with you all the documents that were submitted during your CARBTest appointment request process. These may include a CARB notice, related citations, DMV documents, vehicle repair/conversion invoice paperwork, prior emission compliance test results, etc. Read more about preparing for your appointment. 

Question: Can I still make a CARBTest Referee appointment if my vehicle is in poor operating condition? 

Your vehicle must be in a safe and fully functional condition for CARBTest to inspect the vehicle. Be sure that the oil level is not low, the vehicle is not overheating, etc. Some of the reasons CARBTest may not be able to properly inspect the vehicle include: 

• Safety issues determined by California Highway Patrol (CHP) 

• Low oil level 

• Fuel leak 

• Coolant leak 

• Excessive oil leak 

Question: How long does a CARBTest appointment usually take? 

Appointments are scheduled for 50 minutes. Some services may require a longer time. The CARBTest Referee inspector will inform you beforehand if your CARBTest appointment is anticipated to be more than 50 minutes. 

Question: What if my vehicle does not pass the CARBTest Referee inspection? 

If your vehicle does not pass a CARBTest inspection, the CARBTest Referee Tester will provide you with a CARBTest Vehicle Inspection Report containing guidance on how to resolve the issue. Please remember that the inspector cannot perform diagnostics or repairs. CARB retains the right to review all tests and determine pass or fail. In some cases, CARB may take several days to provide the final inspection results after further review. Schedule a follow up CARBTest inspection once repairs or issues have been resolved. Please visit https://carbtest.org.  

Question: Where do I go to get more CARBTest Referee information? 

Please visit https://carbtest.org. 

Question: How do I pay a CARB Citation? 

CARBTest can only provide independent evaluations. Please review the information on the citation and contact citations@arb.ca.gov or HDVehicleEnforcement@arb.ca.gov with any questions you may have. Visit https://ww2.arb.ca.gov/payment-portal-webform to pay your citation.