What was found
AFTER START ON MASTER RECALL, CONTROL CABIN ZONE TEMP AMBER LIGHT ON. GOES OUT WITH RESET. GROUNDED - YES. PERFORMED PZTC BITE ON BOTH CONTROLLERS REF B737-900 FIM 21-62 TASK 801. FOUND FLIGHT DECK TRIM VALVE FAULTING ON BIT AND PREV. FLIGHT. PUSHED VERIFY AND GREEN GO LIGHT ILLUMINATED. FOUND CABIN TEMPERATURE SENSOR DIRTY WITH DUST/ DEBRIS. CLEANED CONTROL CABIN TEMP SENSOR REF B737-900 AMM 21-61-10. PERFORMED OPS TEST OF PACKS FOR 15 MINUTES. NO DEFECTS NOTED.