As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
C HYD SYS PRESSURE MESSAGE ON EICAS. PERFORMED QRH PROCEDURE. YAW DAMPER KICKED OFF & NOTICED DIFFERENCE IN FLIGHT CONTROL PERFORMANCE. PRESSURE WENT TO ZERO ON BOTH CENTER ELECTRIC PUMPS. RECEIVED CTR HYD EICAS MESSAGE & IAW QRH SHUT OFF CTR PUMPS. DURING TROUBLESHOOTING, FOUND C HYD SYS LOW MESSAGE ON HYD PAGE OF EICAS. REPLACED RESERVOIR DEPRESSURE VALVE, RESERVOIR PRESSURE RELIEF VALVE, C HYD SYS PRESSURE TRANSMITTER IAW AMM 29-11-25, 29-11-24 & 29-31-01.