As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APPROACH RECEIVED MASTER CAUTION ON EICAS "PK BRAKE HANDLE NOT RELSD". SWITCH LIGHT "ON" LIGHT FLASHING INTERMITTENTLY. RAN QRH, DIVERTED TO JFK, DECLARED EMERGENCY. LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE EMERGENCY/PARKING BRAKE PRESSURE SWITCH IAW EMB 175 MM 32-44-09.