As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. LEFT MID EMERGENCY POWER SUPPLY UNIT INOPERABLE, DURING CIDS OPERATIONAL CHECK, TASK 33-51-00-710-001. MAINTENANCE REPLACED LEFT MID EMERGENCY POWER SUPPLY UNIT PER AMM 33-51-38 AND PERFORMED SATISFACTORY OPERATIONAL CHECK.