EPA, CARB, and a patchwork of state programs make diesel compliance moving target. Here's the 2026 snapshot.
Most violations aren't from old equipment — they're from tampered aftertreatment, illegal deletes, or out-of-region operations of non-compliant trucks.
EPA covers federal emissions for new engines and aftertreatment integrity. CARB layers a state-specific in-use program: Clean Truck Check (smog-test-style program for HD trucks in CA), Advanced Clean Trucks (manufacturer ZEV mandate).
DPF/SCR delete kits, tampered DEF sensors, missing EPA labels, missing CARB compliance label, operating non-compliant trucks in CA, ID-only resellers.
Race-only/closed-course is the narrow exception — but resale, road use, and most parts catalog sales are illegal under federal law.