What was found
AT FL310, THE PASSENGER DOOR OUTER HANDLE CAUTION MESSAGE APPEARED. COMPLIED WITH QRH, MESSAGE PERSISTED AFTER INNER HANDLE PULLED. DIVERTED, MESSAGE CLEARED AT 10,000 FT. CLEANED HANDLE AND INTERROGATED PSU, FOUND DI-13 FAULT CLEARED, PERFORMED OPS CHECK AND PRESSURE OF ACFT IAW FIM 52-11-03 AND AMM 212200 OPS CKS GOOD. REMOVED PLACARD AND MEL.