Hi Mike,
Welcome to the forum.
I am assuming that you have proved that the sensor is faulty, and that you do not have a wiring fault.
The ECU uses the fuel temperature to compensate for fuel density, so if it cannot "see" the sensor, then perhaps it will go into limp mode.
I have carried out some research, and find that Fiat eLearn is inconsistent regarding the fuel temperature sensor. I have previously noted that it is not even shown on some engine management wiring diagrams for the 2.8jtd.
I cannot find any details for the sensor under the 2.8jtd heading, but the 2.0jtd uses the same ECU, Bosch EDC 15C7. Details are given for the fuel temperature sensor on the 2.0jtd. 2400 Ohms at 25C, decreasing to 270 Ohms at 80C. Perhaps a temporary resistor of 1000 ohms plugged into the sensor connector at the filter housing, would prove that the sensor failure is the cause of the limp mode. ANY SUCH TEST WOULD BE AT YOUR RISK.
For a more permanent replacement perhaps a used item like
this from Ebay? Do check as to how the pipework can be reconnected.