As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REPEAT FAULT HYDRAULIC PRESSURE DEM 1 ON TAXI OUT. CREW SET ENGINE PUMP TO OFF THEN SELECTED AIR DRIVEN PUMP TO ON & SYSTEM PRESSURE DROPPED TO 700 PSI. AIR DRIVE PUMP 1 NOT PRODUCING HYDRAULIC PRESSURE. FAULT MESSAGE 29037. REPLACED HYDRAULIC PUMP & PRESSURE SW PRECAUTIONARY.