As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA FLIGHT NR 2244: ON APPROACH, NR 1 ENGINE HYD PUMP CAUTION ILLUMINATED WITH A DROP OF NR 1 HYD PRESSURE TO 0. PRESSURE RETURNED TO 3000 PSI WITH SELECTION OF STANDBY HYD PUMP. CAUTION EXTINGUISHED MOMENTARILY, BUT ILLUMINATED WHEN FLAPS WERE SELECTED. MAINTENANCE REMOVED AND REPLACED NR 1 HYD SYSTEM EDP AND NR 1 ENGINE HYD NACELLE SHUTOFF VALVE. FLUSHED NR 1 HYD SYSTEM IAW Q400 AMM 29-10-00 PAGES 319-321. NO FURTHER DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.