A method of monitoring exhaust gas flow through an exhaust system of an internal combustion engine comprises the steps of generating a flow efficiency value (KE), comparing the flow efficiency value to a reference efficiency value, and if the reference eff...

The characteristics of an output of an exhaust gas sensor (5) with respect to an air-fuel ratio of an engine (1) are expressed according to a quadratic function, and the parameters of the quadratic function are sequentially identified according to a sequen...

The characteristics of an output of an exhaust gas sensor with respect to the air-fuel ratio of an engine (1) are expressed by a nonlinear function such as a quadratic function or the like, and the parameters of the nonlinear function are sequentially iden...

During the regeneration of a NOx storage catalyst (3), the point in time at which a lambda probe signal performs a jump is determined. The amount of regenerant agent supplied up to this jump is a measure of a NOx useful storage capacity. This is the capaci...