As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CONTROL CABIN ZONE TEMP LIGHT ILLUMINATED WITH MASTER CAUTION. THE LIGHT EXTINGUISHED WITH RESET. ACFT GROUNDED. PERFORMED A PACK/ZONE TEMP CONTROLLER BITE IAW AMM 21-61-00-700-806-002, FOUND A FLT DECK TRIM VALVE LIGHT WITH THE NR 2 CONTROLLER. REPLACED THE CONTROL CABIN TRIM AIR MODULATING VALVE IAW AMM 21-61-21/401. OPS CHECKED GOOD. ETOPS GROUND VERIFICATION SUCCESSFUL.