What was found
DURING CRUISE, RECEIVED A MASTER WARNING "CABIN ALT". COMPLIED W/ QRH. FL380. CABIN ALT 11,000' DPSI 7.0. USED MANUAL PRESSURIZATION MODE TO CONTROL & STABILIZED CABIN ALT. "CABIN AUTO INOP" CAUTION MSG. COMPLIED W/ QRH PROC. "CABIN ALT AUTO 1" AND "CABIN ALT AUTO 2" STATUS MSG'S.(<P>T/S PER FIM 21-31 FT 803. LOW FLOW INDICATED ON BITE TEST ASU, PER FIM, FOUND LH ENG PRSOV. R/R LH ENG PRSOV, LEAK & OPS CHK OK PER AMM 36-11-09. AS A PRECUATION, R/R CABIN PRESSURE CONTROL PANEL, DUE TO LANDING ACT SET KNOB SLIPS. OPS CHECK NORMAL IAW AMM 21-31-01.</P>)