Method of estimating a variation of a quantity of soot accumulated in a particulate filter

A method of estimating a variation of a quantity of soot accumulated in a diesel particulate filter (285, Figure 1) coupled to an internal combustion engine (110, Figure 1). The method comprises a passive-regeneration check 600 for checking whether a passive regeneration of the diesel particulate filter (285) is occurring and the method provides for performing the steps of: determining an initial quantity of soot SLL* that has accu­mulated in the diesel particulate filter (285) when the passive regeneration began. De­termining a rough variation SLL_var* of the quantity of soot accumulated in the diesel particulate filter (285). Determining an engine speed (ES, Figure 6) and an engine load (EL, Figure 6). Using the engine speed (ES), the engine load (EL) and the initial quantity of soot SLL*, to de­termine (Figure 6) a correction C and calculating the variation SLL_var of the quantity of soot accumulated in the diesel particulate filter as a function of the rough variation SLL_var* and the correction C.