As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#2480, EWR-BOS. (AIRCRAFT PERFORMED AN AIR TURN BACK TO EWR) 'AFTER TAKEOFF ECS SYSTEM ONLY BLEW HOT AIR. CABIN TEMPS REACHED 43C. TEMP CONTROLS SET TO FULL COLD/18C AND ECS IS UNRESPONSIVE TO CHANGES. SLIGHT DECREASE IN TEMPS WITH REDUCED THROTTLE TRIED JUST PACK 1 AND JUST PACK 2 BUT SAME RESULT; REMOVED AND REPLACED FWD TRIM BYPASS VALVE IA AMM 21-62-05. SYS OPS CHECK NORMAL.'