If it's a diesel, it's not a throttle body, its a shut-off butterfly valve that is used to stop the engine running on due to residual fuel (or oil/egr deposits) when turned off.
The "throttle" pedal on the diesel just provides signals to the ECU that are proportional to pedal position. There are two signals for safety. If these are different it will produce an error. It's possible that the new sensor as not installed / set-up correctly or could be faulty.
What are you using to read the code? If it's a generic reader the code descriptions can be misleading. Restting the self learnt functions on the ECU may help. Using
Multiecuscan or similar Fiat specific software to look at the pedal sensor votages would be a good next move. Other possible faults are bad connection, intermittent short to ground or possibly an ECU fault.
Robert G8RPI