As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - FLT 6089 THE CREW REPORTED AN AIR/GROUND FAIL MESSAGE AFTER TAKEOFF. THE AIRCRAFT RETURNED TO ORD AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND REPLACED THE NOSE WHEEL WOW PROXIMITY SWITCH AND CONNECTOR. OPERATIONAL CHECKS WERE GOOD.