As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, CREW ATTEMPTED TO RETRACT LANDING GEAR, RECEIVED A LDG AIR/GND FAIL MESSAGE ON EICAS AND THE GEAR WOULD NOT RETRACT. THE AIRCRAFT RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE PLACED THE AIRCRAFT ON JACKS AND CYCLED THE LANDING GEAR BUT WERE UNABLE TO DUPLICATE THE FAULT. THE LANDING GEAR ELECTRONIC UNIT WAS REPLACED AS A PRECAUTION.