As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: APU BLEED SUPPLYING BOTH PACKS AND ENGINE BLEEDS OFF, A BURNT GUN POWDER SMELL WAS OBSERVED SIMULTANEOUSLY WITH AN OBVIOUS TEMPERATURE INCREASE. THE LEFT PACK LIGHT ILLUMINATED. REMOVED AND REPLACED LEFT HAND ACM. PER J/C 08L00021001.