Method for diagnosing fault in oxygen sensor e.g. wideband sensor, of vehicle, involves increasing error count when actual ratio is different from desired ratio and diagnosing fault when error count is greater than predetermined value

摘要

The method (302) involves increasing an error count (310) when an actual air/fuel ratio is different from desired air/fuel ratio, and selectively adjusting the error count based on actual engine speed, where an oxygen sensor generates a signal indicating the actual air/fuel ratio. Fault in the oxygen sensor is diagnosed when the error count is greater than a predetermined value. A multiplier is determined based on ratio of the actual engine speed to the desired engine speed. The error count is increased at a rate based on mass flow rate of air and the actual engine speed.