As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 1100, RDU TO JFK, AIR RETURN TO RDU DUE L2 PAX DOOR OPEN INDICATION ON EICAS. RAN CHECK LIST ONLY ONE INDICATOR WAS GREEN, RETURNED TO FIELD. ITEM PLACED ON MEL 52-70-01 COND 2 CAT C. [08-06-07] FOUND L2 DOOR AFT VISUAL-LOCK INDICATOR RETAINING RING MISSING. THIS CAUSED THE INDICATOR TO BIND AND NOT SHOW AN ACCURATE INDICATION. INSTALLED NEW RETAINING RING AS PER AMM REF 52-12-22, L2 DOOR INDICATION CHECKS GOOD ON DOOR AND ON EICAS DISPLAYS STATUS PAGE