As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN PRESSURE WILL NOT HOLD MANUAL AC W/ OUTFLOW VALVE FULL CLOSED AND CARGO HEAT VALVE CLOSED WOULD NOT CONTROL PRESSURE. REPLACED AVIONICS COOLING AND OUTFLOW VALVE, NO HELP. (S/N 3147) OFF, (S/N 4400) ON, (P/N 254708948). REPLACED BOTH PNEU FLOW CONTROL VALVE ASSYS RAN ENGS PER PFHB A/C PRESSURIZATION SYS CHECK NORMAL PER M/M. NOTE, A/C INSPECTED FOR PRESSURE LEAKAGE AND NO PROBLEMS FOUND A/C RTS.