Calibration of lambda sensors in exhaust system including NOx sensor downstream of three-way catalyst, first adjusts mixture to approach predetermined NOx signal

摘要

In stoichiometric operation, measurements are taken from sensors. As a function of the gradient of lambda value and of the NOx signal, mixture composition is influenced (NOx led control) until a given value for the NOx signal is reached and/or until the gradient of the NOx signal is less than a threshold value. In addition, the signal at the lambda sensor up to this point, i.e. the calibration point, is allocated a value of lambda = 1 or approximately 1, as the calibration. An Independent claim is included for corresponding apparatus used to carry out calibration.