As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: PERFORMING TRANSIT CHECK HAS BEEN FOUND 4L DOOR EMERGENCY POWER ASSIST SYSTEM PACK GREEN LIGHT OFF. REMOVED AND REPLACED 9V BACK-UP BATTERY ON PASENGER ENTRY DOOR 4L AND ACCOMPLISHED A SATSIFACTORY OPERATIONAL CHECK PER AMM 52-11-20.