As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN PRESS MASTER WARNING ON CLIMBOUT AT 13500'. UNABLE TO CONTROL PRESSURE IN AUTO & MANUAL. DIVERTED AND ACCOMPLISHED A UNEVENTFUL LANDING. REMOVED FROM SERVICE. REPLACED ECU IAW Q400 AMM TASKS 21-61-01-000-801/400-801 OPS CHECKS GOOD A/C PRESSURIZATION SYS OP CHECKS GOOD IAW Q400 AMM TASK 21-31-00-720-801. RETURNED TO SERVICE.