Narrative:

Upon climbing through FL360 to FL380 we received an engine-indicating and crew-alerting system (EICAS) warning 'door passenger aft open'. We [reset] warning and called the flight attendant (flight attendant) to determine status of door. They stated that it was closed and secure yet the top right green indicator had some white area in it that was not normal. We checked the quick reference handbook (QRH) for required actions. We continued to climb to assigned FL380. After leveling off at FL380 we were encountering light to moderate chop turbulence. The warning message came on again. We called again to confirm with the same answer. We requested lower as the door was still indicating unsafe. As we descended we noticed that the differential pressure was 8.3. We referenced the QRH for proper differential pressure for that altitude and determined that the aircraft was indicating a high differential pressure for the altitude we were flying. At this time you could feel the pressure on our ears and the captain asked me if I could feel this as well. I confirmed the discomfort. The warning was still on and had unreliable pressure readings combined with physical discomfort from the pressure. The captain stated 'I think we need to get lower and divert'. This also was confirmed by the QRH if we lost cabin pressure. I confirmed the need to divert. We descended to 14;000 ft. We continued to have pressure fluctuations during the descent. Aircraft was inspected by contract maintenance and deferred. Captain suggested we fly back at 10;000 ft to avoid issues if the pressurization failed. We did so attempting to manage pressure manually and automatically [to ZZZ1]. The aircraft continued to have increase and decreased differential pressure for the flight [to ZZZ1]. Unknown cause for event. The warnings and pressure issues may have been caused by the door open indications.

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Original NASA ASRS Text

Title: E-175 flight crew performed a precautionary landing after troubleshooting a pressurization door issue.

Narrative: Upon climbing through FL360 to FL380 we received an Engine-Indicating and Crew-Alerting System (EICAS) warning 'DOOR Passenger AFT OPEN'. We [reset] warning and called the Flight Attendant (FA) to determine status of door. They stated that it was closed and secure yet the top right green indicator had some white area in it that was not normal. We checked the Quick Reference Handbook (QRH) for required actions. We continued to climb to assigned FL380. After leveling off at FL380 we were encountering light to moderate chop turbulence. The warning message came on again. We called again to confirm with the same answer. We requested lower as the door was still indicating unsafe. As we descended we noticed that the differential pressure was 8.3. We referenced the QRH for proper differential pressure for that altitude and determined that the aircraft was indicating a high differential pressure for the altitude we were flying. At this time you could feel the pressure on our ears and the Captain asked me if I could feel this as well. I confirmed the discomfort. The warning was still on and had unreliable pressure readings combined with physical discomfort from the pressure. The Captain stated 'I think we need to get lower and divert'. This also was confirmed by the QRH if we lost cabin pressure. I confirmed the need to divert. We descended to 14;000 ft. We continued to have pressure fluctuations during the descent. Aircraft was inspected by contract maintenance and deferred. Captain suggested we fly back at 10;000 ft to avoid issues if the pressurization failed. We did so attempting to manage pressure manually and automatically [to ZZZ1]. The aircraft continued to have increase and decreased differential pressure for the flight [to ZZZ1]. Unknown cause for event. The warnings and pressure issues may have been caused by the door open indications.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.