What is Clean Truck Check?+
Clean Truck Check (CTC) is a CARB program for periodic emissions inspections of most non-gasoline heavy-duty vehicles operating in California, including out-of-state trucks.
How often do I need to test?+
The cadence depends on whether your truck submits via OBD or smoke opacity, and on CARB's current schedule for that vehicle class. Most owners receive a notification through their CARB CTC account.
What's the difference between OBD and smoke opacity testing?+
OBD testing pulls data electronically from your engine controller — required for most 2013+ heavy-duty diesels. Smoke opacity is a tailpipe test typically used for older or non-OBD-eligible vehicles.
Who is a 'Certified Tester'?+
A Certified Tester is a person or business that CARB has authorized to perform Clean Truck Check inspections. CTC Connection mirrors CARB's public for-hire Certified Tester list.
Are mobile Certified Testers allowed?+
Yes. Many Certified Testers offer mobile service and will come to your yard. You can filter the directory for mobile-only Certified Testers.
What happens if I miss a deadline?+
Non-compliance fees apply and can lead to DMV registration holds. Submit as soon as possible and contact CARB if you need guidance on resolving a hold.
Is CTC Connection affiliated with CARB?+
No. CTC Connection is an independent directory. We are not the California Air Resources Board and do not issue credentials. Always confirm rules with CARB directly.