As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED RUNAWAY PACK HIGH TEMP FOLLOWED BY SMOKE TOILET CAUTION MESSAGE DURING TAXI OUT. CREW RETURNED TO GATE. MAINTENANCE TROUBLESHOT, REMOVED AND REPLACED RIGHT HEAT EXCHANGER AND RIGHT COALESCER AND PERFORMED CHECKS USING AIRCRAFT MAINTENANCE MANUALS. AIRCRAFT RELEASED FOR SERVICE.