CARB

📖 YOUCANIC Automotive Glossary

CARB (California Air Resources Board) is the California state agency that sets vehicle emissions standards which are typically more stringent than federal EPA requirements. Under the Clean Air Act, California has special authority to set its own emissions standards, and other states can choose to adopt either federal or California standards. Currently, approximately 15 states follow CARB standards, meaning manufacturers effectively design all vehicles to meet CARB requirements since it covers such a large market share. CARB mandates directly drove the development of OBD-II, catalytic converter requirements, EVAP system monitoring, and the progression toward zero-emission vehicle mandates.

For DIYers, CARB compliance affects which aftermarket parts are legal in CARB states — catalytic converters, cold air intakes, headers, and ECU tunes must carry a CARB Executive Order (EO) number to be legal for street use in California and CARB-adopting states. Non-CARB-compliant parts can cause emissions test failure even if they do not trigger a check engine light. CARB-state vehicles also have additional OBD-II readiness monitor requirements that affect emissions test pass/fail criteria.