What was found
ZONE TEMP CONTROL CABIN ILLUM ON RECALL THEN RESETS WITH MC RESET. GROUNDED - YES. PERFORMED PZTC BITE REF B737-900 FIM 21-62 TASK 801. CONTROLLER 2 FAULTED FLT DECK TRIM VALVE. PUSHED VERIFY AND GREEN GO LIGHT ILLUMINATED. FOUND FLIGHT DECK TEMP SENSOR COVERED IN DUST. CLEANED TEMP SENSOR REF B737-900 AMM 21-61-14. OPERATED BOTH PACKS. NO FAULTS ON MASTER CAUTION RECALL. PERFORMED PZTC BITE. NO FAULTS.