What was found
CONT CAB "ZONE TEMP" CAUTION LIGHT AFTER PUSHBACK AND ENGINE START. CLEARS UPON PRESSING MASTER CAUTION PUSH TO RESET. GROUNDED-YES. CONFIRMED LIGHT ON RECALL. PERFORMED PZTC BITE, REF B737-900 AMM 21-61-00. PZTC NR 2 SHOWS FLIGHT DECK TRIM VALVE FAULT ON BIT AND PREV FLIGHT, FAULT CLEARS ON VERIFY. DUE TO HISTORY ON 01/03/21, REMOVED AND REPLACED CONT CABIN TRIM AIR MODULATING VALVE, REF B737-900 AMM 21-61-21. OPERATION CHECKS GOOD, REF AMM 21-61-00. LEAK CHECK GOOD, ETOPS GROUND VERIFICATION SUCCESSFUL.