As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT BLEED DUCT LEAK LIGHT ILLUMINATED IN FLIGHT. FOLLOWED QRH PROCEDURES BUT DUCT LEAK LIGHT REMAINED ON. SHUT DOWN LEFT ENGINE AS PER QRH. RETURNED TO LAX. DUPLICATED PROBLEM ON GROUND AFTER 5 MINUTES AT CLIMB POWER. REPLACED LT 18 PSI REGULATOR. RAN AT CLIMB POWER FOR 15 MIN. OPS CHECK GOOD.