As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RIGHT PACK LIGHT ILLUMINATED. PERFORMED QRH WITH TRIP RESET, PACK LIGHT REMAINED ON. ACFT GROUNDED. BITE OF RIGHT PACK/ZONE TEMP CONTROLLER (PZTC-2) IAW FIM 21-62 TASK 801. SHOWED NO FAULTS, BUT LEFT PACK/ZONE TEMP CONTROLLER (PZTC-1) SHOWED CONTROLLER FAULT - STANDBY PACK WHICH RESET WITH VERIFY TEST. REMOVED, REPLACED, AND TESTED PZTC-1 IAW AMM 21-61-20-000-801 AND AMM 21-61-20-400-801. OPS NORMAL.