As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING TAXI-OUT, HYD 1 LO PRESS MESSAGE CAME ON. THE CREW REPORTED LOUD BANG FROM AFT PART OF CABIN. CREW EXECUTED RELEVANT ABNORMAL CHECKLISTS AND RETURNED TO RAMP. AFTER VERIFICATION BY THE MTCE CREW, THEY FOUND OUT THAT THE NR 2 HYDRAULIC ACCUMULATOR SEPARATED. (TC NR 20070707001)