As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED LEFT FUEL HEAT INDICATION DURING CLIMBOUT. HAD TO PUSH LEFT ENGINE THROTTLE UP TO KEEP OIL TEMP LESS THAN 135 DEGREES AND FUEL HEAT WOULD NOT GO OFF. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED LEFT ENGINE FUEL HEAT VALVE. SYSTEM GROUND CHECK NORMAL OPERATION.