Hi Voodles
You'll need to wake up those sensors to see what the actual reading is, we've found -50 bar as a placeholder value before, then once the sensors are awake, standard 2.5-3bar is displayed.
If this value is displayed after wakeup, it's most likely an issue with the sensor not transmitting it's reading correctly. There isn't a way for us to calibrate the sensor, we can only learn it to the ECU.
Kind regards
Ruan