As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH R PACK DEFERRED, LEFT PACK HI PRESS ON CLIMB OUT FOLLOWED BY CABIN ALT WARNING. COMPLIED WITH QRH. RETURNED TO FIELD. (FLT 5113) CLOSED REMOVED AND REPLACED LEFT PACK PRSOV, IAW AMM. OPS AND LEAK CHECKS GOOD, COMPLIED WITH OPERATIONS PROCEDURE ON GROUND FOR BLEED SWITCHING IAW MEL FOR RIGHT PACK DEFERRAL. NO LEFT PACK HI PRESS NOTED.