As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4202 THE CREW REPORTED THE RECEIVED A LAND AIR GROUND FAIL MESSAGE AFTER TAKEOFF. THE LANDING GEAR DID NOT RETRACT. THE CAPTAIN ELECTED TO RETURN TO ORD. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE LANDING GEAR ELECTRONIC UNIT IAW EMB 145 AMM 32-32-01. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.