As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, THE FLIGHT CREW REPORTED THAT THEIR WAS AN INTERMITTENT LANDING GEAR AIR/GROUND FAIL MESSAGE DISPLAYING ON THE EICAS. THE CREW RETURNED TO KORD AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE NOSE LANDING GEAR WOW PROXIMITY SWITCH CORRODED WITH A PIN EXTRACTED. REPLACED THE NOSE LANDING GEAR WOW PROXIMITY SWITCH AND THE NOSE LANDING GEAR WOW HARNESS. OPERATIONAL CHECKS WERE GOOD WITH NO FURTHER DEFECTS NOTED.