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 THE EMERGENCY POWER SUPPLY UNIT BITE TEST MAINTENANCE FOUND EMERGENCY POWER SUPPLY UNIT 10WL FWD L/DEV-B(300RH1) FAULT MESSAGE. MAINTENANCE SECURED LOOSE CONNECTOR AT 2870VC AND ACCOMPLISHED A SATISFACTORY BITE TEST.