Hopefully OP will reply to clarify if those posted values were actual readings via the IID or calculated.

My next step would be to ask the GAP tech support.

My 'need' for the value in mbar, or any pressure value, is not essential.
It would be useful for me to compare the measured pressure differential over my DPF right after cleaning - by the company that cleaned it - to current values.
A sensor voltage value of a known clean DPF would also work, of course.
With clean I mean cleaned, not regenerated to low gram (this I can now do myself )

The workshop procedure doesn't mention a calibrated pressure gauge, I agree with you it would be better.
It would also mean a true calibrated current value has to be entered as 'zero'.
Quote form the workshop manual:

Quote:

The following conditions must be met to allow the differential
pressure sensor offset value to be learnt and stored: Using the manufacturer approved diagnostic system,
clear DTCs from engine control module, then monitor the datalogger signal 'sump oil temperature -
measured' ensuring a minimum of 50 degrees C is achieved. Start engine, run above 500RPM for 2
minutes, then a further 30 seconds at idle. Ensure the engine cooling fan is not running. Set vehicle in park
and set ignition status to off. Wait 30 seconds for the engine control module to power down, learn and
store differential pressure sensor offset value. This process must be carried out six times, to allow a large
negative offset value to adapt back to 0 Hpa

AFAIK the OP sold his L322 and moved to another make so may no longer be active. 2012 TDV8 Vogue (L322)