As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3719 -PRESS- DIVERTED TO LAX DUE TO UNABLE TO MAINTAIN CABIN PRESSURIZATION. LEFT BLEED PRESSURE LOST. CORRECTIVE ACTION: MAINTENANCE REPLACED PRESSURE SENSE LINE TO PRECOOLER CONTROL VALVE AND PRECOOLER CONTROL VALVE PER B737 AMM 36-12.