As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER START AND AFTER BLEED SWITCHES ON (AND PACK SWITCHES ON) WE HAD A "ZONE TEMP" LIGHT THAT CAME ON FOR THE CONTROL CABIN WITH MASTER CAUTION RECALL AND WENT OUT FO WITH RESET. GROUNDED - YES. INITIAL EVALUATION FOUND #2 PACK/ZONE TEMP CONTROLLER SHOWING FLT DECK TRIM VALVE FAULT. PERFORMED PACK/ZONE TEMP CONTROLLER BITE TEST REF B737-800 AMM TASK 21-61-00-700-806-002, NO DEFECTS NOTED, TEST PASSED AND FAULT WAS RESET. RAN BITE TEST 2 MORE TIMES NO DEFECTS NOTED.