What was found
RETURNED TO DEPARTURE DUE TO A MECHANICAL ISSUE, LOW PRESSURE ON ENGINE 1 AFTER TAKEOFF. EMERGENCY WAS DECLARED, FLIGHT WAS NOT OVERWEIGHT, AND LANDED WITHOUT FURTHER INCIDENT. "ENG 1 OIL LO PR" ON ECAM. WINDMILL FOR 15 MINUTES, OIL PRESSURE 0 FOR 15 MINUTES. DUE TO EIU FAULT HISTORY OIL PRESSURE TRANSMITTER REQUIRES REPLACEMENT. THE AIRCRAFT WAS GROUNDED. REPLACED OIL PRESSURE TRANSMITTER IAW MM 79-33-15, OPERATIONS CHECK OK.