As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3869 THE CREW REPORTED THAT AFTER TAKEOFF THE LANDING GEAR FAILED TO RETRACT. THE CREW RECEIVED A MASTER CAUTION LANDING GEAR DISAGREE MESSAGE ON EICAS. THE CAPTAIN DECLARED AN EMERGECNY AND ELECTED TO RETURN TO ORD. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE LANDING GEAR SELECTOR VALVE AND ADJUSTED THE STEERING VENTERING PROXIMITY SWITCH PX37. THE OPERATIONAL CHECK AND LEAK CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.