As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFT CABIN ZONE TEMP LIGHT ON MASTER RECALL. GROUNDED - YES. C/W FIM PROCEDURES. BITE TEST OF 1 & 2 PZTC = PZTC 1 FAULTED ZONE TRIM VALVE. GREEN GO / VERIFY LIGHT ILLUMINATED AND RESET FAULT. OPERATED BOTH R & L PACKS WITH NO FAULTS NOTED. REF B737-800 FIM 21-62 TASKS 844, 801, & 835.