As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 4340, AFTER TAKEOFF SELECTED THE LANDING GEAR LEVER UP AND RECEIVED EICAS LANDING GEAR AIR/GND FAIL MESSAGE FOLLOWED BY EICAS E 1-2 REV FAIL MESSAGE. COMPLETED CHECKLIST AND DECIDED TO RETURN TO DEPARTURE. DECLARED AN EMERGENCY AND THE LANDING GEAR CYCLED NORMALLY. LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REMOVED AND REPLACED THE LANDING GEAR ELECTRONIC UNIT IAW AMM 32-32-01. OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.