As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - CREW RETURNED TO FIELD WHEN AFTER TAKE-OFF, THE AFT CARGO DOOR CAUTION ILLUMINATED WITH A STATUS MESSAGE THAT READ PROX SYSTEM FAULT 2. PSI DIFFERENTIAL WAS SEVEN. MAINTENANCE INSPECTED THE AIRCRAFT AND ADJUSTED THE PROX SENSOR AND LUBED THE AFT CARGO DOOR HANDLE. AN OPERATIONAL CHECK AND GROUND PRESSURIZATION WAS PERFORMED. NO DISCREPANCIES WERE NOTED. AIRCRAFT WAS RETURNED TO SERVICE.