As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTURE, THE NR 2 FUEL TEMPERATURE WAS FLUCTUATING FROM PLUS 30 TO MINUS 60 DEGREES. AIRCRAFT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. FOUND FUEL TEMPERATURE SENSOR DEFECTIVE. REPLACED SENSOR. ENGINE TUNE-UP CHECKED OK. AIRCRAFT RETURNED TO SERVICE.