As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RAPID RISE IN DIFF PRESS URE. CABIN PRESSURE DECREASED INTO NEGA TIVE. REF FIM 21-31 TASK 801 PERFORMED BITE CHECK OF DCPC 1 AND 2. FOUND ACTIVE FAULT ON DCPC 1, CAB PRESS SW ACTIVE MESSAGE. NO FAULTS FOUND ON DCPC 2. REF FIM TASK 21-31 TASK 820 FOR CAB PRESS OUTFLOW VALVE ALTITUDE SWITCH ACTIVITY, PERFORMED REMOVAL AND REPLACEMENT OF AFT OUTFLOW VALVE ASSY REF AMM 21-13-03. PERFORMED OUTFLOW VALVE INSTALLATION TESTS ON BOTH DCPC CONTROLLERS REF TASK 21-31-00-710-801 & 802. OPS CHECKS NORMAL. NO FAULTS PRESENT AT THIS TIME.