As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF WHEN RETRACTING GEAR, CREW RECEIVED LEFT MAIN GEAR DISAGREE AND GEAR DOOR MESSAGE. CREW CYCLED GEAR AND SAME INDICATION REMAINED. FLIGHT RETURNED TO DTW AND COMPLETED AN UNEVENTFUL LANDING. DTW MAINTENANCE PERFORMED OPERATIONAL CHECK PER MM AND COMPLETED 12 NORMAL GEAR SWINGS. MAINTENANCE CALLED AIRCRAFT OK FOR SERVICE. NWA MAINTENANCE CONTROL FOLLOWED UP THIS EVENT WITH LOG TO CHANGE GEAR SEQUENCE VALVE AND THE GEAR DOWNLOCK ACTUATOR AS A PRECAUTIONARY MEASURE.