As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AIRCRAFT WAS IN HEAVY CHECK MAINTENANCE FOUND THE EMERGENCY RAM AIR VALVE CHECK VALVE CORRODED ON THE RIM. MAINTENANCE REMOVED AND REPLACED THE EMERGENCY RAM AIR CHECK VALVE IAW EMB 175 21-25-03. THE AIRCRAFT IS OUT OF SERVICE IN HEAVY CHECK.