As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT PASSING 18;000. ENG 1 A & B SYS HYD LOW PRESSURE PUMP LIGHT ILLUMINATED. CHECKED HYD OIL QTY & PRESSURE, A SYS PRESSURE WAS DROPPING. CONSULTED QRH CHECKLIST 13:4 LOSS OF A SYS. COMPLETED CHECK LIST AND RETURNED TO DEPARTURE. HYD CHECKED BRAKES PRIOR TO APPROACHING GATE. REMOVED AND REPLACED THE NR 1 HYDRAULIC ENGINE DRIVEN PUMP. INSPECTED AND REPLACED THE NR 1 ENGINE CASE DRAIN FILTER IAW AMM 29-11-11. A/C OK FOR SERVICE.