As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT TOP-OF-DESCENT RECALL CHECK CONT CAB ZONE TEMP LIGHT ILLUMINATED. THE LIGHT EXTINGUISH UPON MASTER CAUTION PUSH -TO-RESET. GROUNDED - YES. ACCOMPLISHED PACK/ ZONE TEMP CONTROLLER BITE TEST REF B737-900 AMM 21-51-00, #2 CONTROLLER SHOWS FLIGHT DECK TRIM VALVE ON BIT AND PREVIOUS FLIGHT. ACCOMPLISHED FIM 21-62 TASK 832 CONTROL CABIN TRIM AIR VALVE FAULT ISOLATION, VERIFY TEST ON #2 CONTROLLER, SHOWS GO. GROUND VERIFICATION SHOWS GOOD.