Patent ID: 8359826

Claim:
An NO x sensor trouble diagnosis device that is provided in an exhaust gas passage of an internal combustion engine and detects a concentration of NO x in exhaust gas passing through the exhaust gas passage, the device comprising: an exhaust NO x flow rate calculator and storage apparatus for calculating and storing an exhaust NO x flow rate discharged from an internal combustion engine per unit time; a detected NO x concentration apparatus for storing a detected NO x concentration detected by an NO x sensor; and a trouble determining apparatus means for defining a reference pattern as a time-lapse variation reference of the exhaust NO x flow rate and a follow pattern as a time-lapse variation reference of the detected NO x concentration detected by the NO x sensor, and determining whether the detected NO x concentration undergoes a transition while having a predetermined relation with the follow pattern when the exhaust NO x flow rate undergoes a transition while having a predetermined relation with the reference pattern in a case where the internal combustion engine is in a normal operation mode, to determine the responsiveness of the NO x sensor.