What was found
AIRCRAFT WAS GROUNDED: SEVERAL NAVIGATION FAILURES INCLUDING, MAP, TRACK, TERRAIN FAIL, PROXIMITY WARNING SYSTEM FAIL, TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM FAIL. BOTH NAVIGATION DISPLAY DID NOT DISPLAY HEADING DATA AT GATE, MECHANIC FOUND AIR DATA INERTIAL REFERENCE UNIT- L DATA INVALID, DECLARED EMERGENCY. AND RETURNED TO MIA. FLIGHT WAS OVER WEIGHT FOR LANDING. FOUND FAULT CODE 34-45071 IN OMF, ACCOMPLISHED PER IFIM 34-45-00, MESSAGE SHOWS NOT ACTIVE, INTERMITTENT FAULT, ALL REQUIRED TESTS PASSED, NO FAULTS.