As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: FAULT OF EPSU-EMERGENCY POWER SUUPLY UNIT 11WL DURING OPERATIONAL TEST OF EMERGNECY LIGHTS IN PASSENGER CABIN. REPLACED EPSU-EMERGENCY POWER SUPPLY POSITION 11WL IN PASSENGERCABIN IAW AMM 33-51-38-000-001-A STEP 3 THRU STEP 4, AND AMM 33-51-38-400-001-A STEP 3 THRU STEP 4, AND 5A(2)(B). OPERATIONAL TEST ARE OK.