Upstream temp sensor
The upstream temp sensor will be located somewhere between the turbo and the catalytic converter and informs the ECM of the temperature of the exhaust gases after they have passed through the turbo upstream of the catalytic converter
You may at times see some radical temperature sensor readings of approx-3500°c while using Bosch actual data.
This type of reading will be a default setting of the ECM as an open circuit of the temp sensor. With this type of reading the Regeneration phase will not be able to take place.
A good starting point before attempting a Regeneration is to check the temp sensor readings as you could be waisting time.