As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED TO MTX WHILE SITTING AT THE GATE LEFT PACK AUTO FAIL FOLLOWED BY LEFT PACK OVERHEAT CAUTION COCKPIT STARTED FILLING UP WITH SMOKE. ISSUED PACK MEL REMOVED AND REPLACED AIR CYCLE MACHINE IAW 21-51-00. AIRCRAFT RETURNED TO SERVICE.