Find Clean Truck Check
testing services near you.
CTC Connection is the independent directory of CARB Clean Truck Check Certified Testers. Search by ZIP, city, or state — and learn how to walk in prepared.
Search by ZIP or city
Filter by location and the exact CTC services you need — OBD, smoke opacity, or mobile.
Sourced from CARB
Records mirror CARB's public for-hire Certified Tester list with regular refreshes.
Plain-English guides
Drive cycles, readiness monitors, deadlines, and how to prepare for a passing test.
Browse Certified Testers by state
Jump straight to Certified Testers in your operating region.
Compliance resources
Walk into your test prepared. Pass on the first try.
Drive cycle guide
How to complete a heavy-duty diesel drive cycle so monitors are ready before testing.
Read guideReadiness monitors
What each OBD monitor means and how to clear an 'incomplete' status.
Read guidePrep for your test
A checklist to maximize your chances of passing OBD or smoke opacity.
Read guideOBD testing
On-board diagnostics submission for model year 2013+ heavy-duty diesel vehicles.
Learn moreSmoke opacity (non-OBD)
Required for older heavy-duty diesels that can't submit via OBD.
Learn moreMobile Certified Testers
Certified Testers that come to your yard. Filter the directory for mobile-only.
Learn moreThis directory is not affiliated with or endorsed by CARB. Certified Tester information is sourced from CARB’s public for-hire Certified Tester list when available; inclusion on that list is optional. Always confirm Certified Tester credentials, services, and availability before scheduling compliance testing.