OBD vs. smoke opacity testing

CARB’s Clean Truck Check program has two technical pathways for proving a heavy-duty diesel vehicle is meeting emissions standards. Which one applies depends on the model year and onboard diagnostics capability.

OBD submissions

For model year 2013 and newer heavy-duty diesels. The vehicle’s on-board diagnostics data is read and submitted electronically. AIRPASS automates this entire workflow.

Smoke opacity (non-OBD)

For older heavy-duty diesels that can’t submit OBD data. A Certified Tester uses an opacity meter at the tailpipe. Filter thedirectory for smoke opacity Certified Testers.

Which one applies to my truck?

2013 model year or newer heavy-duty diesel → OBD submission (AIRPASS-eligible).
Pre-2013 heavy-duty diesel → smoke opacity test at a Certified Tester.
Motor homes have specific rules; many Certified Testers note motor-home testing on the directory.

This 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.