As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#188, LAX-BOS. (ETOPS) 'APX 45 MINS INTO FLIGHT AT CRUISE EXPERIENCED AIR PACK 2 REGUOL FAULT. LEFT PACK ON PER QRH; PER TSM 21-61-00-810-825-A REPLACED PACK 2 OUTLET TEMP SENSOR REF AMM 26-61-11. FIN: 32HH. ER GROUND VERIFICATION PASSED.