As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) EICAS (ENGINE INDICATION AND CREW ALERT SYSTEM) MESSAGE FOR DISAGREEMENT FOR LANDING GEAR RETRACTION, (FOR UP LOCK) AIRCRAFT RETURNED TO LAND IN PHILADELPHIA AFTER QRH PROCEDURE APPLIED.AFTER INSPECTION, FOUND THE UP LOCK TARGET TO BE LOOSE. RE-TIGHTENED THE TARGET, GEAR SWING COMPLETED, LANDING GEAR CHECKED SERVICEABLE.