As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 7827, IAD TO CMH - AFTER TAKEOFF, CREW ATTEMPTED TO RAISE THE LANDING GEAR AND RECEIVED A "LG AIR/GND FAIL" MESSAGE AND THE GEAR WOULD NOT RETRACT. THE FLIGHT RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE TROUBLESHOT THE FAULT TO THE LGEU USING THE CMC. THE LGEU WAS REPLACED AND THE TEST FLIGHT WAS SUCCESSFUL.