As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BURNING SMELL IN COCKPIT AND SMOKE IN THE AFT CABIN (ENGINE 2 WAS RUNNING PACK 2 ON BEING SUPPLIED BY APU AND PACK 1 OFF DEICING WAS NOW REQUIRED FOR FLIGHT). NR 2 ACM SEIZED. R & R ACM. OPERATIONS CHECK SATISFACTORY. NO SMOKE NOTED WHEN RUNNING PACKS.