Abstract: The process includes the operations of: arranging a particular filter (PT) in the exhaust duct (EP), generating, by indicator devices (S1-S5), electrical signals indicative of the values of parameters (NQ) of the operation of the engine (ICE); performing filter regeneration phases of the filter (PT) by controlling the injectors (I1-I4) of the engine (ICE) in such a way as to cause a controlled increase in the temperature of the exhaust gas so as to cause combination of the particulates accumulated in the filter (PT), identifying on the basis of signals provided by at least some of the indicator devices (S1-S5) the type of journey or trip (MPi) currently being made by the motor vehicle form among a plurality of predefined types of journey or trip (MP1-MP4); calculating, according to a predefined estimation function, and in dependence on the instantaneous type of journey or trip (MPi), the quantity (Q) of particulates gradually accumulated in the filter (PT); and starting a filter regenerating phase of the filt

Abstract: The diagnostic method includes the steps of: generating a pressure signal related to the fuel pressure of an injection system of an engine; comparing the pressure signal with a reference pressure value; determining a fuel leakage condition of the injection system when the pressure signal is less than the reference pressure value; reducing the quantity of fuel injected into the cylinders of the engine in the presence of the leakage condition; calculating a share value contributed by each cylinder to the work torque value generated by the engine; comparing each share value with a respective reference share value; determining a jammed-open injector condition when at least one of the share values is greater than the respective reference share value; and determining a supply circuit failure condition when the share values are all less than the respective reference share values.