Cal. Penal Code § 1396

If an accusatory pleading is filed, the corporation may appear by counsel to answer the same, except that in the case of misdemeanors arising from operation of motor vehicles, or of infractions arising from operation of motor vehicles, a corporation may appear by its president, vice president, secretary or managing agent for the purpose of entering a plea of guilty. If it does not thus appear, a plea of not guilty shall be entered, and the same proceedings had thereon as in other cases.