As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SAN - AT 23,000 FEET DURING CLIMB-OUT, APU FIRE WARNING ILLUMINATED. FIRED EXTINGUISHER BOTTLE. LIGHT REMAINED ON. DECLARED IN-FLIGHT EMERGENCY. FLIGHT DIVERTED TO LAX. FOUND FIRE WARNING MODULE HAD FAILED. REMOVED AND REPLACED FIRE WARNING MODULE. (X)