As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4891, CREW REPORTED DURING TAXI AND WITH APU ON RECEIVED EICAS PACK 2 OVERHEAT ACCOMPANIED BY A BURNING ODOR. AIRCRAFT REMOVED FROM SERVICE. PERFORMED OPERATIONAL CHECK OF RIGHT PACK SYSTEM. NO DEFECTS NOTED. SUSPECT DUAL TEMP CONTROL VALVE. REMOVED AND REPLACED DUAL TEMP CONTROL VALVE. AIRCRAFT RETURNED TO SERVICE.