In brief Check air and fuelling before you condemn the turbo or DPF. This English page pairs with the French article; it does not replace a test.
What it usually means
A diesel that puffs black is burning rich or starving for air: dirty filter, boost leak, injector, EGR, or a turbo that is no longer packing air. The French article’s job is that symptom, not a generic turbo explainer — that lives on the part sheet.
Keep driving hard on black smoke and you can coke the turbo and load the DPF. That still is not a reason to guess the part from the sofa.
Translation of the live French article. Not a diagnosis. Service intervals stay with the manufacturer.