As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT & RT DUCT PRESSURE SPLIT DURING CRUISE, WITH ENGS RUNNING, LT & RT ISOL VLVS CLSD & BLEED SW ON. CREW COMMENTS: IN CRUISE FL330 LT DUCT PSI = 15 AND RIGHT DUCT PSI = 28. EPR, N1'S MATCHED. LT ENG PRESS BELOW NORMAL. LOCKED OUT LT ENG HPSOV. RPL- :AIR MODULE BIT SHOWED PRC. REPLACED PRC PER FIM, FIG 108 AND AMM. ALSO WRENCH CHECKED ALL LINES BETWEEN PRESS CONTROLLER AND VALVE. FOUND SENSE LINE SLIGHTLY LOOSE AT FAN AIR PLENUM.