As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ASH 2667 PHF TO CLT, THE CREW HAD THE NR 2 PACK PRODUCING A BURNING SMELL WHILE THE APU WAS SUPPLYING BLEED AIR ON THE GROUND. MAINTENANCE REMOVED AND REPLACED THE HIGH PRESSURE DUCTS AND OVERTEMP SWITCH. THE AIRCRAFT DEPARTED WITHOUT FURTHER INCIDENT.