As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
"C HYD SYS PRESS" EICAS MSG APPEARED IN FLIGHT. THE FLIGHT CREW VERIFIED NO OTHER ABNORMALITIES WERE ASSOCIATED WITH THE SYSTEM. AFTER FOLLOWING QRH PROCEDURES, THE FLIGHT CREW DECLARED AN EMERGENCY AS PRECAUTION ALTHOUGH NO EMERGENCY ACTION WAS REQUIRED PER THE QRH PROCEURES. NO SYSTEM DEFECTS WERE NOTED DURING THE OPERATIONAL CHECKS BY MX. THE CENTER HYD PRESSURE SWITCH WAS REPLACED AS A PRECAUTION.