What was found
(CAN) CABIN PRESSURE WARNING LIGHT ILLUMINATED THROUGH 19,500 FT. DESCENDED TO 12,000FT AND CAB PRESS HOLDING. PRESSURIZATION CONTROL SEEMS TO BE U/S IN AUTO AND MANUAL. DURING MAINTENANCE TROUBLESHOOTING, CDS SHOWS L CHANNEL 3001 PAC FCV REF FIM 21-60-00810-809, CONNECTOR 2121-P23 ON FLOW CONTROL VALVE SHOWS OPEN BETWEEN PINS, A AND B. VALUE SHOULD BE 50 TO 200 OHMS. SERVO ON FLOW CONTROL VALVE IS FAULTY. FLOW CONTROL VALVE REPLACED IAW AMM 21-52-01-000-801 AND 21-52-01-400-801. ENGINE RUN UP COMPLETED, BOTH BLEED SYSTEMS, FLOW CONTROL OPERATE NORMALLY. ACFT PRESSURIZED TO 5.5 PSID. NO FAULTS.