As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EICAS MESSAGE. C HYD SYS MAINT DISPLAYED. ACCOMPLISHED TROUBLESHOOTING ADDRESSING 'C' HYD MAINT MESSAGE. SYSTEM CHECKS GOOD PER TEST. PRESSURE STILL FLUCTUATES. REPLACED ADP MODULATING VALVE, NO HELP. REPLACED ADP PRESSURE REGULATOR AND SHUTOFF VALVE PER MM. REPLACED CENTER PRESSURE TRANSMITTER PER AMM. OPS AND LEAK CHECK OK.