As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER PUSHBACK AND ENGINE START: MASTER CAUTION GAVE AIR COND WITH ZONE TEMP. THIS RESET WITH MASTER CAUTION PUSH TO RESET. THE ZONE TEMP WAS CONT CAB. GROUNDED - YES. RELEASED PER MEL 21-21G FLIGHT DECK PRIMARY TEMP CONTROL INOP. ACCOMPLISHED ZONE TEMP CONTROL BITE B737-800 AMM 21-61-00 GRD VERIFICATION SUCCESSFUL THIS CLEARS MEL 21-21G.