As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED. WHILE PERFORMING L37 EMERGENCY LIGHTNING FUNCTIONAL CHECKS RECEIVED CLASS 1 ERROR FPEEPMS AISLE LT EPSU 15WL DOOR 3. SWAPPED EMERGENCY POWER SUPPLY UNIT WITH 13WL. PERFORMED GOOD BITE TEST. SWAPPED UNITS TO ORIGINAL POSITION WITH POSITIVE BITE TEST.