As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NOSE LANDING GEAR RED UNSAFE LIGHT REMAINED ON AFTER GEAR WAS RETRACTED. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. REPLACED NOSE GEAR PROXIMITY CONTROL UNIT AND DOWNLOCK SENSOR. CYCLED GEAR SEVERAL TIMES. OPERATIONAL CHECK OK. AIRCRAFT RETURNED TO SERVICE.