What was found
AIRCRAFT WAS GROUNDED: EMERGENCY DECLARED; AIRCRAFT LANDED WITHOUT INCIDENT, DECISION WAS MADE TO RETURN TO LAX, AFTER TAKEOFF ON DEPARTURE AND DURING FLAP RETRACTION NOTICED FLAP ASYMMETRY AND IMMEDIATELY RESET FLAP LEVER TO 1. HELD AND RAN QRH PROCEDURE AND AFTER BURNING FUEL AND DECLARING AN EMERGENCY. T/S FLAP ASYMMETRY FAULT IAW FIM TASK 27-59-00 FOUND FLAP SKEW SENSOR NR 4 FAULT CODE 27-53253 SKEW RESOLVER OUT OF TOLERANCE. REMOVED AND REPLACED NR 4 SKEW SENSOR IAW AMM 27-59-01.