As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT EXCURSION FROM TAXIWAY. CREW REPORTED LOSS OF BRAKES AND STEERING. PFR SHOWS BRAKE SELECTOR VALVE 23GG FAULT ALONG WITH MLG HYDRAULIC PIPE MESSAGE. TEST RUN ON BSCU CHANNEL 1 & 2. BSCU CHAN 1 LAST LEG REPORT - "BRK SELECTOR VALVE (23GG)/L G HYDRAULIC PIPE". LRU WIRING & BSCU TEST - "NO FAULT DETECTED". NORMAL BRAKING TEST - "NO FAULT DETECTED". GROUND SCAN - "NO FAULT DETECTED". SUSPECT 23GG VALVE IS LEAKING INTERNALLY, REPLACED SAME. PHASE 1 CHECKS, NO DAMAGE NOTED.