uzintheair
The FADEC uses TAT for several functions - including ratings calculations and scheduling the variable stator vanes (VSV).
safetypee
Not sure what 'initially had problems" you're speaking of. The TAT probes on GE (and CFM) engines are not heated - and hence not susceptible to ICI (ice crystals are an issue on heated surfaces - which melt the ice which then rapidly re-freezes). Both Pratt and Rolls have had issues with inlet probes icing up in ICI conditions - but they are heated due to the pressure sensor.
The GEnx engine core had issues with ICI - ice would form in the compressor then shed, which could flameout the engine and damage compressor blades.
We had a separate issue with the inlet TAT probe - basically the probe was not very good and we had large probe to probe variations in readings (the probe was new and unique to the GEnx). So GE changed back to the TAT probe used on the GE90 - and the original TAT probes were replaced (there was a compliance time period allowed but has long since passed).