As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EICAS DISPLAYED DE-ICE SYS AND DE-ICE SYS ALT, WHEN PNEUMATIC BOOT DEICING SYS WAS SELECTED ON NORM AND ALTERNATE. MX TROUBLESHOOTING IDENTIFIED THE PRESSURE REGULATOR VALVE AS DEFECTIVE. VALVE WAS REMOVED AND REPLACED WITH NEW VALVE. FUNCTIONAL CHECKED SATISFACTORY. ACFT RETURNED TO SERVICE.