As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE TAXIING FOR TAKEOFF IN ORD, WE GOT A "BRAKE 50% DEGRADED" AMBER CAS MESSAGE. WE RAN THE QRH. THE CAS MESSAGE WOULD GO AWAY WITH PARKING BRAKE APPLIED.BUT SWOULD RETURN WITH PB OFF. THIS CAS MESSAGE STAYED ON FOR THE ENTIRE TAXI BACK TO SIGNATURE. REMOVED AND REPLACED OB BRAKE CONTROL VALVE IAW AMM 32-41-35. PERFORMED LEAK AND OPS CHECK IAW AMM 32-41-00 NO DEFECTS NOTED.