As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF ON GEAR RETRACTION, THE LEFT MAIN LANDING GEAR WOULD NOT RETRACT, INDICATION LEFT MAIN GEAR DOWN AND LOCKED WITH GEAR DOOR IN THE OPEN POSITION. AIRCRAFT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. REPLACED THE LEFT DOOR SEQUENCE VALVE AND LEFT MAIN GEAR DOOR ACTUATOR. LUBRICATED THE LEFT LANDING GEAR AND PERFORMED EXTENSION AND RETRACTION TEST, OPERATIONAL CHECK OK.