What was found
FLIGHT AIR RETURNED TO LAX DUE TO A GEAR DISAGREE MESSAGE ON RETRACTION AT 400 FT. QRH 13.3 PERFORMED GEAR DID NOT RETRACT, LEVER PLACED IN DOWN POSITION, ALL 3 GEAR GREEN. CREW CONFIRMED GEAR. NO EMERGENCY DECLARED. LANDING GEAR EXTENSION & RETRACTION OPERATIONAL TEST PERFORMED, NO DEFECTS NOTED. REMOVED AND REPLACED PROXIMITY SENSOR ELECTRONIC MODULE 1 IAW PER AMM 32-61-01. REMOVED AND REPLACED CONTROL LEVER, LANDING GEAR IAW AMM 32-33-01. OPS CHECK GOOD. LG EXTENSION AND RETRACTION SYSTEM OPS CHECK REQ. PERFORMED LANDING GEAR EXTENSION AND RETRACTION SYSTEM (ON JACKS) OPERATIONAL TEST IAW AMM 32-33-00710-801-A. OPS CHECK GOOD.