California Air Resources Board

The Periodic Smoke Inspection Program (PSIP) and the Heavy-Duty Inspection and Maintenance Program (HD I/M) Clean Truck Check are inspection and smog check programs to ensure polluting, poorly maintained heavy-duty vehicles operating in California are quickly identified and repaired.

PSIP requires fleet owners to conduct annual smoke opacity inspections of diesel vehicles over 6,000 pounds (lbs.) Gross Vehicle Weight Rating (GVWR), and to repair those with excessive smoke emissions to ensure compliance. PSIP requirements carry forward through 2023 until periodic testing required by Clean Truck Check (HD I/M) begins.

Clean Truck Check (HD I/M) is a smog check program for heavy-duty trucks where owners of most non-gasoline powered trucks over 14,000 lbs. GVWR that operate in California will perform periodic inspections to ensure trucks are operating as intended. Phased in implementation began in January 2023 with periodic testing beginning in the 2024 time frame. Until periodic testing begins, truck owners will still need to complete PSIP testing and keep the records as specified in the PSIP regulation.