METHOD FOR MONITORING THE FUNCTIONING OF AN NOx SENSOR ARRANGED IN AN EXHAUST GAS CHANNEL OF AN INTERNAL COMBUSTION ENGINE

摘要

The invention relates to a method for monitoring the functioning of an NOx sensor (18) which is arranged in an exhaust gas channel of an internal combustion engine and which is located downstream from an NOx storage catalytic converter (16). The aim of the invention is to detect the faulty functioning of the NOx sensor in a simple manner in order to be able to take appropriate measures if necessary. To this end, the mass of NOx absorbed by the NOx storage catalytic converter (16) is determined within a diagnostic period using a measurement signal of the NOx sensor (18) while, at the same time, an absorbed NOx specified mass is calculated using a model for the NOx storage catalytic converter (16), and a ratio of the NOx mass to the NOx specified mass (control value KWn) is compared to the predetermined limit values (Gnu, Gno). The aim of the invention is also accomplished by measuring a duration (tmes) for a complete NOx regeneration of the NOx storage catalytic converter (16), by calculating a specified duration (tmod) for the NOx regeneration using a model for the NOx storage catalytic converter (16) and using a measured or calculated NOx load state, and by comparing a ratio of the duration (tmes) to the specified duration (tmod) (control value KWt) with predetermined limit values (Gtu, Gto).