Catalytic convertor downstream gas sensor failure detection in motor vehicle exhaust monitoring systems, compares successive monitored outputs with upstream sensor outputs after statistical processing to remove signal noise

摘要

An arrangement for registering the malfunction of a sensor located downstream of a catalytic convertor (25) in the exhaust system of a combustion engine, has a control unit (5) configured to determine a ratio Kact between the amplitude of a first output signal (P14), from an oxygen sensor (17), and a second output signal (P4) of an upstream air-fuel composition sensor (16). The control unit compares successive signals from each of the two sensors, and undertakes statistical processing e.g. by successive least-squares regressions, to remove the effects of signal noise, particularly over the frequency range 3- 7Hz, before deciding if the sensor remains healthy. Independent claims are included for: methods of detecting sensor failure with the arrangement.