As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RECEIVED CABIN ALT WARNING MESSAGE DURING CLIMB OUT. CAB ALTITUDE REACHED 10,000FT. PERFORMED QRH PROCEDURES AND RETURNED TO LAX. PERFORMED CPC TEST IN THE MDC TEST PASSED PRESSURIZED AIRCRAFT PER AMM 21-31-00-910-801 PRESSURIZATION CHECKS GOOD ON THE GROUND AT THIS TIME.