What was found
AIRCRAFT NOT GROUNDED - EMERGENCY DECLARED - SHORTLY AFTER TAKE-OFF, FORWARD CARGO DOOR INDICATION ON ECAM (REPEAT ISSUE). RETURNED TO DEPARTURE STATION, OVERWEIGHT LANDING WITHOUT FURTHER INCIDENT. CHECKED FORWARD CARGO DOOR, VERIFIED CLOSED AND LOCKED. APPROVED, FORWARD CARGO DOOR. OK FOR SERVICE. REMOVED AND REPLACED FORWARD CARGO DOOR PROXIMITY SENSOR (30WV) PER AMM 52-71-00, AND ACCOMPLISHED ADJUSTMENT OF SENSOR, OPERATIONAL CHECK GOOD, BITE CHECK - NO FAULTS.