As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#454, PBI- JFK. (AIRCRAFT PERFORMED AN AIR TURN BACK) IN CRUISE AT FL310 L BLEED FAIL AMBER CAUTION CAME ON WITH BLEED ON MEL. RAN ECC AND PROBLEM REMAINED AIR SYNOPTIC PAGE VALVE OPEN 9 PSI IN AMBER. AIR RETURN TO PBI; REMOVED AND REPLACED #1 ENG PRESSURE REGULATING SHUTOFF VALVE PER AMP BD500-A-J36-11-01-00AAA. OPS AND LEAK CHECK GOOD. A/C OK FOR SVC.'