As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT TOD MASTER CAUTION RECALL, THE "CONT CAB ZONE TEMP" LIGHT ILLUMINATED. FOLLOWED QRH PROCEDURE. GROUNDED - YES. ACCOMPLISHED PZTC BITE PER B737-900 AMM 21-61-00-700-806-002. #2 CONTROLLER FAULTED FLT DECK TRIM VALVE. REMOVED CONTROL CABIN TRIM AIR VALVE PER AMM 21-61-21-000-801. INSTALLED TRIM AIR VALVE PER AMM 21-61-21-400-801.INSTALLED. PERFORMED ZONE TRIM AIR MODULATING VALVE OPS CHECK PER AMM SUBTASK 21-61-21-860-007 OPS TEST PASSED.