As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE TAXIING IN, THE "LOW BRAKE PRESSURE" AND "ANTI SKID INOP" AMBER MESSAGES ILLUMINATED. A FEW SECONDS LATER, THE BRAKE PEDALS WENT TO THE FLOOR AND WE HAD ALMOST NO BRAKES. NO BREAKERS WERE TRIPPED. SIGN OFF. REMOVED POWER BRAKE RELIEF VALVE CAUSING LOW PRESSURE P/N 1785-2 S/N 1371 AND INSTALLED OVH BRAKE RELIEF VALVE, IAW 560XLS AMM CH 32-44-20. OPERATIONS CHECK GOOD.