As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NOSE LANDING GEAR WOULD NOT RETRACT AFTER TAKEOFF. RED UNSAFE LIGHT WAS ALSO ILLUMINATED AND LOUD RUMBLE WAS HEARD. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. FOUND NOSE LANDING GEAR STRUT UNDERSERVICED. SERVICED STRUT TO PROPER LIMITS. OPERATIONAL CHECK OK ON GEAR SWING. AIRCRAFT RETURNED TO SERVICE.