Differential Pressure Measurement at CJCD

I previously thought that the soot load of the diesel particulate filter (DPF) was determined by measuring the pressure difference across the DPF. However, it seems that this can also be achieved by measuring the pressure difference against the outside air pressure.
In my specific CJCD system, the "differential pressure sensor" is only connected to the engine side of the DPF; the other connection on the sensor is just a short, open hose. The RLF (presumably a diagnostic tool) shows something different.
hg
Herbert.

Correct, in a properly sized exhaust system, there isn't much pressure change after the DPF – and that small amount can be modeled using a calculation model.

Incidentally, a "calculation model" is a) cheaper than connecting to the DPF and b) more reliable because nothing can mechanically break.

Best regards, Rainer.

"In principle, it is possible if you know the resistance of the rest of the exhaust system, the exhaust flow (based on exhaust temperature, air mass, and injection quantity), and the external pressure. The air pressure sensor is probably located in the engine control unit (ECU). There is no air pressure sensor shown in the wiring diagram."
hg
Herbert.

Quote:

The air pressure sensor is likely located in the MSG

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Okay, I understand. Please provide the German text you would like me to translate into English. I will only provide the translation.