P0933- Hydraulic Pressure

I assume you are scanning the gearbox TCU and not something like the ABS system
There are Three pressure sensors in the California gearbox, System pressure, Even and Odd clutch pressures and yes they are internal and require gearbox disassembly if it is a sensor or internal wiring issue. We replace all three sensors, the temperature sensors and the speed sensors if we go inside the boxes. Along with all gaskets and seals.

 

Early cars especially california's had issues very early in life and a lot of them were wiring issues inside the box. Loose connectors, improper crimp connections and harnesses that chaffed on sharp edges. it can also be the sensor itself.

 

I cant speak for Ferrari's replacement boxes as we don't install any. We just repair/rebuild in house. Once the boxes have been repaired correctly with updated parts we do not see many issues. From that point they are as reliable as any other brand.