What was found
ONT - ABORTED TAKEOFF - FLT 0083 - ON TAKEOFF ROLL AT ONT EN ROUTE FOR PHX RECEIVED ECAM MESSAGE HYDRAULIC GREEN ENGINE 1 PUMP LOW PRESSURE, REJECTED TAKEOFF AT 70 KTS AND RETURNED TO GATE. VERIFIED GREEN HYDRAULIC SYSTEM QUANTITY AND PRESSURE, ISSUED MEL 29-30-04, COND. 6, NR 1 ECAM ENGINE PUMP LOW PR INDICATIONS INOP. WHEN AIRCRAFT ARRIVED IN PHX MAINTENANCE REMOVED AND REPLACED NR 1 ENGINE HYDRAULIC PUMP LOW PRESSURE SWITCH IAW AMM 29-11-17, OPERATIONAL CHECK WAS GOOD.