Exhaust gas oxygen sensor monitoring

The sensor malfunction monitor of claim 9, wherein the oxygen sensor is a UHEGO sensor and the signal is a lambda signal.

An engine management system for an internal combustion engine, the engine management system comprising a sensor malfunction monitor operable to detect an asymmetric malfunction manifested in a lambda signal output by an oxygen sensor in an exhaust system of the internal combustion engine, the sensor malfunction monitor being operable to determine a turning point of a signal from the oxygen sensor to determine a measurement timing for verifying the operation of the oxygen sensor.

An internal combustion engine system comprising an internal combustion engine, an exhaust system, an oxygen sensor in the exhaust system and a sensor malfunction monitor, the sensor malfunction monitor being operable to determine a turning point of a signal from the oxygen sensor to determine a measurement timing for verifying the operation of the oxygen sensor.

A method of detecting a sensor malfunction, the method comprising:

• measuring a rate of change of a signal sensor from the sensor on detecting a turning point of the signal;
• and
• determining a measurement timing for verifying the operation of the oxygen sensor.

The method of claim 16, wherein the turning point is a change in direction of the signal from signal from one of an increasing or decreasing signal to the other of an increasing or decreasing signal.