As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK - NR 1 HYD SYS LOW QTY CAUTION, THEN SHORTLY AFTER GOT A NR 1 HYD PUMP FAIL WARNING MSG. CFR WAS CALLED. AC LANDED SAFELY WITHOUT INCIDENT. REMOVED AND REPLACED O-RING ON STEERING CONTROL UNIT IAW EMD 145 AMM 29-10-13, LEAK CHECK GOOD.