What was found
CONTROL CABIN ZONE TEMP LIGHT ILLUMINATES W/ MASTER CAUTION, AND RESETS W/ MASTER CAUTION. GROUNDED - YES. PER B737-800 FIM 21-62 TASK 842, #2 ZONE TEMP CONTROLLER SHOWS FAULT OF FLIGHT DECK PRIMARY TRIM VALVE. FURTHER T/S PER FIM 21-62 TASK 842 BITE TEST OF PZTC 1 AND 2 REF B737-800 AMM 21-61-00-700-806-002. NO FAULTS NOTED AND BOTH PZTC 1 AND 2 SHOW GREEN GO LIGHT. RAN APU PACKS FOR 5 MIN AND NO FLIGHT DECK FAULTS NOTED.