As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHILE PERFORMING PS CHECK W/C: 26L00005005, OPS TEST OF EMERGENCY LIGHTS FAILED WITH FAULT CODE "EPSU UNIT EMER R". EPSU PWR SPLY UNIT 12WL UNIT FAULT. MAINTENANCE REPLACED EPSU PWR SUPPLY UNIT AND BATTERY. REF AMM 33-51-38.