California Code of Civil Procedure > Code Civ. Proc. §116.740. Defendant’s Motion to Vacate Judgment for Improper Service
(a) If the defendant was not properly served as required by Section 116.330 or 116.340 and did not appear at the hearing in the small claims court, the defendant may file a motion to vacate the judgment with the clerk of the small claims court. The motion shall be accompanied by a supporting declaration, and shall be filed within 180 days after the defendant discovers or should have discovered that judgment was entered against the defendant.
(b) The court may order that the enforcement of the judgment shall be suspended pending a hearing and determination of the motion to vacate the judgment.
(c) Upon a showing of good cause, the court may grant the motion to vacate the judgment. If the plaintiff is not present, the court shall hear the motion in the plaintiff’s absence.
(d) Subdivisions (d), (e), and (f) of Section 116.730 apply to any motion to vacate a judgment.