Risk of Particle Filter Clogging

[Jamie@SPTuning]

The lower part of the downpipe contains the actual DPF, this unbolts and simply slides out. Just slide in the new replacement DPF. You'll need to reset soot/ash content with a diagnostic tool so the ecu knows there's a new filter fitted.
For the cleaning fluid I would inject it in through where the temperature sensor screws in as this is directly above the top of the DPF cartridge.
The catalyst sits above the dpf in the downpipe so injecting the cleaning fluid into the higher up O2 sensor is not so effective as the cat will soak up a lot of the liquid.
If the car is in limp mode you won't be able to regenerate the DPF whilst driving unless you have diagnostic tool.

[meadowfield]

mine never got fixed, despite being only 2 years old and in warranty. My 3rd DS never did the particle issue, but did do the fan on full speed a lot, especially after motorway driving.

My fourth DS3 blueHDi is behaving after 26K... there I go jinxing it