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Clean Truck Check - Test Results FAQ

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OBD Testing

When performing On-Board Diagnostic (OBD) vehicle emissions test, please ensure that the CARB-certified OBD test device is physically connected to the vehicle, and that the test results appear in your CTC-VIS account prior to releasing the vehicle. 

  • If the OBD test result does not show up in your CTC-VIS account within 5 minutes after completing the test, you may need to re-test the vehicle. 

  • If you have a problem during testing, try: 

  • Unplug all other devices connected to the diagnostic port to ensure they don’t cause communication interferences 

  • Verify the communication between the vehicle and the OBD test device 

  • Ensure the internet connection is stable 

  • If the test result does not appear after multiple attempts during the emissions compliance testing, contact hdim@arb.ca.gov 

For certain OBD test devices, the device vendors may display a test result of ‘Awaiting CARB's Response’ on their own test result portal and there is no test result shown in your CTC-VIS account. We recommend contacting the test device vendor to verify if there are any issues on their end that might have prevented the test from being transmitted and processed in CTC-VIS. If the vendor identifies a potential issue with the submission from our end, please have them reach out to their assigned device certification engineer at CARB for further assistance. 

Also see a more detailed description of OBD Testing Recommended Practices.

Understanding CTC-VIS OBD Test Results

Referee Referral

The vehicle's OBD system appears to not match a certified configuration created by the engine manufacturer. Please obtain any needed repairs to restore the OBD system to manufacturer specifications and then take it to a Clean Truck Check Referee to verify that the OBD system is operating properly. If you have obtained this test result, Referee appointment requests can be made from the vehicle’s CTC-VIS entity account. Please login to your account, then click on “Forms”, navigate to the “Online Forms” tab, then click on the form titled “Referee Appointment Request”. Please select “State-directed Referee Inspection” action listed in the “Referee Appointment Request” form. For additional instructions on requesting an appointment, please visit the informational video at Requesting a CTC Referee Appointment. 

Modified OBD System

For an OBD system that appears to not match a certified configuration created by the engine manufacturer please see  Referee Referral - Modified OBD System

Fail Due to Change in Configuration 

Your test result is invalid due to a data mismatch. Please make sure that a CARB-certified device is plugged into the vehicle, and that the correct vehicle is being tested. 

Invalid Test 

The submitted OBD test is invalid because the OBD testing was done when the vehicle was NOT under idle conditions. Please ensure the engine is running and the vehicle is stationary and perform the test again. 

Invalid Tester Credentials 

The OBD test cannot be accepted because the tester does not have valid credentials at the time the test is scanned.  This is because either the tester credential has expired, or they never took the tester training course and passed the exam. For more information on how to take the tester training and exam, please visit Tester Training Course and Exam. Please also make sure the email address used to create CTC-VIS tester account for the exam MUST match the email address used to log in to your testing device. 

Invalid Software Version 

The scan device software used to collect and submit vehicle OBD data is invalid. It either is not approved by CARB or is out of date and needs to be updated. Please ensure the latest CARB-certified OBD test device’s software version from your OBD test device vendor is installed. You can also contact your OBD test device vendor if the issue persists. For more information on CARB-certified OBD test device software version, please visit Clean Truck Check - OBD Test Devices | California Air Resources Board.  

Not Ready

A vehicle is not ready (and cannot pass an emissions compliance test) if it has not been operated enough since the OBD memory was last cleared (also known as a “code clear”) and thus has not had sufficient time to complete a full diagnostic assessment to determine if an emissions related issue exists. 

A code clear can occur if a fault has recently been repaired, or if a vehicle recently has had a dead, disconnected, or replaced battery. The current minimum operation threshold for a Clean Truck Check emissions test submission is for the vehicle to have at least five (5) Warm-Up Cycles (WUCs) since “codes cleared”. A warm-up cycle means driving a vehicle so that the engine coolant temperature rises by at least 40 degrees Fahrenheit after the engine is started and reaches at least 140 degrees Fahrenheit for diesel engines (160 degrees for alternative fuel engines). 

Do NOT schedule a Clean Truck Check OBD emissions test if codes were recently cleared. Drive the vehicle normally to make sure the vehicle has operated sufficiently to be able to complete the test. For example, 5 warm-up cycles can typically be obtained within a week of driving. For more information, please visit OBD Readiness Criteria. 

Test Results Could Not Be Determined

The submitted OBD test data is incomplete. Please unplug other devices connected to the diagnostic port, verify the communication between the vehicle and the OBD test device, and ensure the internet connection is stable. Note that OBD testing can only be completed on 2013 and newer model year diesel engines and 2018 and newer model year alternative fuel engines. 

If the same result is received after multiple attempts, the Clean Truck Check Referee can assist with vehicles that cannot undergo a standard inspection due to design limitations, malfunctioning components, or compatibility issues. Referee appointment requests can be made from the vehicle’s CTC-VIS entity account. Please login to your account, then click on “Forms”, navigate to the “Online Forms” tab, then click on the form titled “Referee Appointment Request”. Please select “Test Incompatibility/Alternative Test Procedure (vehicle testability issue)” action listed in the “Referee Appointment Request” form. For additional instructions on requesting an appointment, please visit the informational video at Requesting a CTC Referee Appointment. 

Vehicle Not Applicable for OBD Testing 

The tested vehicle does not support OBD test submissions. Please note OBD testing is applicable only to diesel powered vehicles with 2013 and newer model year engines and alternative fuel powered vehicles with 2018 and newer model year engines. Please visit Emissions Compliance Testing Requirements for more information about vehicle testing requirements. 

Fail

The vehicle has failed the OBD emissions test. Please obtain any needed repairs and retest the vehicle. Please note that repairs could result in codes being cleared, and your vehicle might be “Not Ready” (and cannot pass an emissions compliance test) if it has not had enough operation since “code cleared”. However, Clean Truck Check requires you to submit a passing emissions compliance test before the vehicle(s) deadline. 

A code clear can occur if a fault has recently been repaired, or if a vehicle recently has had a dead, disconnected, or replaced battery. The current minimum operation threshold for a Clean Truck Check emissions test submission is for the vehicle to have at least five (5) Warm-Up Cycles (WUCs) since “codes cleared”. A warm-up cycle means driving a vehicle so that the engine coolant temperature rises by at least 40 degrees Fahrenheit after the engine is started and reaches at least 140 degrees Fahrenheit for diesel engines (160 degrees for alternative fuel engines). 

Do NOT schedule a Clean Truck Check OBD test if codes were recently cleared. Drive the vehicle normally to make sure the vehicle has operated sufficiently to be able to complete the test. For example, 5 warm-up cycles can typically be obtained within a week of driving. For more information, please visit OBD Readiness Criteria. 

Testing Results Not Showing

Test results will only show within 90 days of the day the vehicle was added into CTC-VIS.

  • For OBD test submissions: 
    • OBD results take 0-1 days to populate
    • If you do not see your OBD results in that timeframe, please contact your OBD device manufacturer and ask to resend the files to CARB.
  • CTC-VIS only shows OBD compliance emissions tests submitted on or after October 1, 2024.  
  • For OBD test submissions to CARB prior to October 1, 2024, CTC-VIS will not show the submitted test results.  Please check with your tester for the submitted test result information.  
  • For non-OBD test submissions: 
    • Please check the test submission for VIN typos and ask your customer to check their vehicle account for VIN typos. 
      • If the vehicle account has a VIN typo, they need to deactivate the VIN and add a new vehicle with the correct VIN.

All heavy-duty vehicles need to have proof that the engine meets appropriate emissions standards by having the manufacturer ECL properly affixed on the engine and fully legible.  If you are unable to obtain the ECL, you must request the manufacturer write you a letter stating the label is unavailable. Engine information must be provided on the manufacturer's letter.  A copy of the letter must be kept in the cab of the vehicle in a place known to the driver.

Awaiting CARB's Response

We recommend contacting the test device vendor to verify if there are any issues on their end that might have prevented the test from being transmitted and processed in CTC-VIS. If the vendor identifies a potential issue with the submission from our end, please have them reach out to their assigned device certification engineer at CARB for further assistance.