Cal. Bus. & Prof. Code § 9880.2
The following persons are exempt from the requirement of registration:
(d) A person whose primary business is the wholesale supply of new or rebuilt automotive parts who solely engages in the remachining of individual automotive parts without compensation for warranty adjustments to those parts and who does not engage in repairing or diagnosing malfunctions of motor vehicles or motorcycles. “Primary business” means the business that accounts for the majority of the company’s gross sales. “Wholesale supply” means the sale, by a seller who possesses a California Resale Permit, of automotive parts to a retailer or jobber for the purpose of resale. However, a person described in this subdivision, prior to commencing work, shall do both of the following: