As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING A CIDS OPERATIONAL TEST OF THE EMERGENCY LIGHTING SYSTEM, EMERGENCY POWER SUPPLY UNIT 17WL HAD A FAULT MESSAGE. REPLACED BATTERY FOR EMERGENCY POWER SUPPLY UNIT 17WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL; CHECK PER AMM 33-51-38.