As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIVERTED TO SFO DUE TO A BLEED VALVE PROBLEM. *S/D* LEFT ENGINE BLEED SYSTEM WAS CLOSING OFF DUE TO TEMPERATURE. LEFT ENGINE FAN AIR MODULATING VALVE TEMPERATURE SENSOR AND LEFT ENGINE AIR BLEED OVERTEMP SENSOR REPLACED. NO PNEUMATIC WRITE-UPS SINCE DIVERSION.