As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4321 - AFTER TAKEOFF FLIGHT CREW NOTED ENGINE 2 VIBRATION. CREW REDUCED POWER AND NOTED VIBRATION AT 2.0 ON SCALE. CREW RETURNED TO ORD WITHOUT FURTHER INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED ALL FAN BLADES AND REPAIRED FAN INLET. ALSO REPAIRED FAN CONTAINMENT RING PER IAW GE ENG MAN 72-00-23. AIRCRAFT RETURNED TO SERVICE.