What was found
BRK FAIL YELLOW CAS: ON TAXI OUT AT KASG WE HAD A BRAKE FAIL CAS MESSAGE ILLUMINATE. I ATTEMPTED TO USE THE MAIN BRAKES TOO SLOW THE AIRCRAFT TO A STOP AND GOT NO INDICATION OF BRAKING ACTION. AT THAT POINT THE EMER/PARKING BRAKE WAS ENGAGED TO STOP THE AIRCRAFT. THE FBO TOWED US BACK TO THE RAMP. // SIGNOFF// COMPLIED WITH CMC DOWNLOAD AND SENT TO THE CONTACT CENTER I.A.W EMB-505S AMM 45-45-00 COMPLIED WITH FIM 32-41-00-810-813-A RAN-UP #1 AND #2 ENGINES AND OPERATIONAL CHECKED BRAKES WITH NO CAS FAULTS NOTED I.A.W EMB-505S AFM OPENED UP LAV AREA TO GAIN ACCESS TO BCU TO REMOVE FOR TROUBLESHOOTING OPEN BELLY PANEL 194EL TO ACCESS BCM REOVED ALL CONNECTORS FOR TROUBLESHOOTING C/W BLOCK DIAGRAM 1,6,7 REMOVED BCM UNIT WITH FAULT P/N DAP00101-02 S/N 64JN INSTALLED A INSPECTED/TESTED UNIT P/N DAP00101-02 S/N 21KA TSO: 1614 CSO: 1009 LEAK CHECKED AND OPERATIONAL CHECKED/TAXI CHECK WITH NO FAULTS NOTED I.A.W EMB-505S AMM 32-41-07