What was found
WHEN TAXI STARTED, WE HAD BRAKE FAIL YELLOW CAS MESSAGE AND HAD NO BRAKES HAD TO USE EMER BRAK TO STOP. PER MX REQUEST PULLED BREAKER AND RESET BRAKES SEEMED TO WORK FINE AFTERWARD. POTENTIAL ICE OR SNOW CONTAMINATION BASED ON CURRENT WX. REMOVED AND REPLACED BRAKE CONTROL UNIT PERFORMED OPS CHECK OF ALL HYDRAULIC SYSTEMS, NO DEFECTS NOTED. WORK COMPLETED IAW EMB-505 AMM 32-41-07-000-801-A, 32-41-07-400-801-A PN OFF: DAP00101-02, SN OFF: 49KY, PN ON: DAP00101-02, SN ON: 092XE.