As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CONT CAB ZONE TEMP ILLUMINATED AFTER TAKEOFF. FOLLOWED QRH PROCEDURE - ZONE TEMP ILLUMINATES ONLY ON RECALL INDICATING FAILURE OF FLIGHT DECK PRIMARY OR STANDBY TEMP CONTROL AS PER QRH. GROUNDED - YES. PERFORMED PACK ZONE TEMPERATURE CONTROLLER BITE PER B737-800 AMM 21-61-00-700-806-002 #2 CONTROLLER FAULTED FLT DECK TRIM VALVE. REMOVED AND REPLACED FLT DECK ZONE TRIM VALVE PER AMM 21-61-21. INSTALLATION CHECK GOOD.