Failure determination method for O.sub.2 sensor

Details Failure determination method for O.sub.2 sensor Failure determination method for O.sub.2 sensor

1993-07-16

1995-06-13

Williams, Hezron E.

Measuring and testing

Instrument proving or calibrating

Volume of flow, speed of flow, volume rate of flow, or mass...

123688, 731181, G01M 1900

Patent

active

054232031

ABSTRACT:
A failure determination method for an O.sub.2 sensor is provided wherein the air-fuel ratio of a mixture is maintained at a value which produces a leaner or richer air-fuel ratio than a stoichiometric ratio by a predetermined value, for a predetermined time after an engine starts operating in an idle region, to thereby make the oxygen concentration of exhaust gas surrounding the O.sub.2 sensor uniform. Subsequently, the air-fuel ratio is forcibly subjected to an oscillatory change with a predetermined amplitude of .+-.10 to 15% of the stoichiometric ratio with respect to the stoichiometric ratio at a predetermined frequency of several Hz, to determine abnormality of the O.sub.2 sensor based on the change of the output voltage of the O.sub.2 sensor.

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