As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF AUTOTRIM WARNING AND AUTOPILOT DISCONNECT. AUTOTRIM WARNING EXTINGUISHED. CREW NOTED AN UNUSUAL SMELL IN THE FLIGHT DECK. REPORTED, SMELLS LIKE INSULATION. AIR RETURN TO DTW. PERFORMED OP CHECK OF AUTOTRIM SYSTEM. CND PROBLEM. AUTOTRIM OP CHECK GOOD. INSPECTED ELEC BAY, AVIONICS RACK AND FOUND NO DEFECTS. PERFORMED OP CHECKS OF ALL AVIONICS EQUIPMENT. ALL CHECKS GOOD.