The contractor, dealer, or manufacturer shall complete warranty service to correct all substantial defects within 90 days of receiving the buyer’s written notice specified in subdivision (b) of Section 1797.3, unless there are circumstances which are beyond the control of the contractor, dealer, or manufacturer.
Source:
Section 1797.7, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV§ionNum=1797.7..