Pre-2013 model-year engines without OBDs will be required to submit an opacity test and a visual/functional inspection twice a year. The opacity test must be up to the SAE J-1667 opacity standard.

A truck undergoes a Periodic Smoke Inspection Program opacity test in Buellton, Calif. (Beryl Technologies via Twitter) Also, CARB randomly audits fleets, reviews on-site maintenance and ...