As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - FLT 4289 - WHEN THE GPU WAS DISCONNECTED FROM THE AIRCRAFT, THE EMERGENCY LIGHTS CAME ON AND DRAINED THE POWER SUPPLIES. ALL FOUR BATTERY POWER SUPPLIES FOR EMERGENCY CABIN LIGHTING. OPS CHECK GOOD. AIRCRAFT RETURNED TO SERVICE. (M)