In general, state and federal law prohibit modifications to your vehicle’s emission control system. When repairing your vehicle, the emission-related parts used must be original equipment manufacturer (OEM) parts or be replacements for the OEM parts, as specified by the part manufacturer.

Modifications to your emissions controls are not acceptable unless the parts used are approved by ARB. ARB grants approvals in cases where the changes or aftermarket parts do not modify the performance of the emission controls in a way that increases emissions. ARB assigns the approved parts an “executive order” (EO) number that may be used to verify acceptability. ARB provides a listing of EO exempted parts on their Web site at www.arb.ca.gov.

Minor changes that do not affect the connectivity with or operation of other emission controls are acceptable. For example, the installation of an universal replacement hose in place of a preformed hose would be allowed.