As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IMMEDIATELY AFTER TAKEOFF THE CREW RECEIVED A LG AIR/GND FAIL EICAS MESSAGE. THE LANDING GEAR INDICATED 3 GREEN DOWN AND LOCKED WITH THE LEVER DOWN. THE QRH WAS FOLLOWED AND THE ACFT RETURNED AND LANDED WITHOUT INCIDENT. MX CLEANED AND INSPECTED THE LANDING GEAR PROX SWITCHES FOR THE WOW SYS AND THE AIR/GROUND MESSAGE WENT AWAY. A TEST FLIGHT WAS PERFORMED AND NO FURTHER DEFECTS WERE NOTED.