As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COULD NOT COOL AFT CABIN - NO LIGHTS ILLUMINATED. AFT SUPPLY DUCT STAYS AT 28 DEGREES C, AFT CABIN TEMP ( PASS CAB) INDICATES 32 DEGREES C. MX CONTROL TROUBLESHOOT INFLIGHT WAS UNSUCCESSFUL. ACFT GROUNDED. CONFIRMED PROBLEM. RAN VERIFY TEST ON NR 1 ZONE TEMP CONTROLLER - FAULTS AFT PAX CABIN TRIM VALVE. REPLACED NR 1 ZONE TEMP CONTROL VALVE REF MM 21-61-21. AFT CABIN TRIM VALVE, OPS NORMAL, REF MM 21-61-21. ETOPS GROUND VERIFICATION TEST SUCCESSFUL.