As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN RUNS WARM IN ALL PHASES OF FLIGHT. IMPOSSIBLE TO COOL DOWN. GROUNDED - YES. REPLACED ALL 3 CABIN TEMP SENSOR FILTERS WITH NEW ONES REF B737-900 AMM 21-61-06-400-801. ACCOMP CABIN TEMP CONT & IND OPS TEST. CONT CABIN TEST PASS, BUT FWD & AFT PASS CABIN UNCONTROLLABLE STAYS HOT REF AMM 21-61-00-700-807-002. REF L/P#60229979/ AND 60229980, R/H PACK TCV VALVE REPLACED AND L/H PACK CONTROLLER REPLACED. REF B737-900 FIM 21-62 TASK 849 REPAIR CONFIRMATION OPS NORMAL, ALL THREE ZONES COLD.