Date: 202102
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Airspace: Class B ZZZ
Aircraft component: Pressurization Control System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Second reporter function: Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: Auto Press 2 failed and cause the cabin pressure to drop which triggered a Dif Press warning. We requested a lower altitude from ATC and were cleared down. We did not have to deviate. Shortly after the decent Auto Press 1 took over and balanced the pressure out.The cause is unknown the aircraft was downed after landing for the same issue.No more broke planes.


Second narrative: During FFOD power up; we had a 'auto press 2 fail' status message momentarily but it cleared. I didnt think much of it. Cruising at 33;000 ft. about 40mins away from ZZZ; I felt my ears popping a bit and the cabin rate fluctuating from 0 to -500 fpm (back and forth) and lowering the cabin altitude. We eventually got a diff press warning; I was pilot flying. Cabin pressure was normal. I initially mistakenly called the wrong checklist. The FO (First Officer) request lower; and ATC granted it. By the time we pulled out the Quick Reference Handbook for the emer depress warning; auto press 2 fail status came up and our warning was gone. I guess cpc 2 had failed and auto switched to number 1. We leveled off at 24;000 ft. Masks were never worn and priority handling wasn't requested. I called the FAs (Flight attendants) in the back to see if they noticed anything; they said they didn't. Also; when we put flaps 45 on landing; the rate rapidly dropped to -1;000 fpm and back to 0; which isn't normal. I wrote it up in ZZZ in full detail. We were supposed to keep the plane for a AGS turn. Maintenance deferred auto(cabin) press controller 2. Part of our mel had the crew check the manual controller works. When we did; we had a green advisory message about cabin pressure being greater than 8;000 ft. I was on the phone with the ODP; local Maintenance was there; they were talking to Maintenance Control and Maintenance Operation Director; and we didn't know why that message was there and how to make it go away. We ended up doing a plane swap. We trying all kinds of troubleshooting methods but were not successful.


Synopsis: Flight Crew reported loss of CPC2 [Cabin Pressure Controller] caused a descent and subsequent maintenance action; resulting in a plane swap at destination airport.