As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING SINGLE PACK OPERATIONS THE LT A/C PACK SYSTEM WOULD NOT MAINTAIN CABIN PRESSURE. CREW FOLLOWED QRH & WAS ABLE TO RECOVER PRESSURIZATION SYSTEM. PERFORMED PNEUMATIC HEALTH CHECK ON NR 1 ENGINE FOUND HIGH STAGE PILOT & PRESSURE REGULATING & SHUTOFF VALVE FAULT. REPLACED HIGH STAGE PILOT & PRESSURE REGULATING & SHUTOFF VALVE IAW AMM 36-11-08, 36-11-09. RAN NR 1 ENGINE & PRESSURIZED AIRCRAFT WITH SINGLE PACK TO 4 PSID. NO FAULTS.