Device and method for diagnosing the condition of a probe upstream from a catalytic converter

摘要

An apparatus and method for diagnosing the condition of a sensor in an internal combustion engine upstream from the catalytic converter. The diagnosis utilizes a signal from a second non-linear probe downstream from the catalytic converter. This signal is processed to give a signal that is filtered. The filtered signal is in turn compared with maximum and minimum values. The upstream probe is considered to be correct if the signal falls between these two values or faulty if it falls outside the values.