So long as the vehicle is equiped with the original catalytic converter (installed at factory), it will pass the California smog check without modification needed. If at any time the CAT was replacement, the replacement CAT must conform to California Air Resources Board requirements... meaning it must posses an EO number (Executive Order). If the cataytic converter was replacement at some point and the replacement CAT does not have an EO number, it will not pass the emissions inspection in California.