You won't get a code any further in depth than that one, it's already given you the closest it can.
It's showing that the DPF differential sensor reading is too low. You now have to do some testing to find the cause of that low reading.
The first and easiest test is to visually look at the pressure pipes coming from the DPF up to the sensor on the battery box. If they're split or damaged in any way, the sensor readings will be wrong.
If they look ok, you can then run a live data graph in Forscan, showing the DPF sensor readings alongside the RPM and road speed. That will give us an indication of how low the reading is, whether it rises during higher RPM driving, and how low it is when the code is triggered.
That will then give us an idea of whether the sensor may be faulty, or whether the cause of the fault lies elsewhere.
It's not as simple as a code telling us exactly which part needs replacing I'm afraid! This is what you pay garage diagnostic fees for, the code reading is just the start.