Failure diagnostic apparatus and method for air-fuel ratio...

Details Failure diagnostic apparatus and method for air-fuel ratio... Failure diagnostic apparatus and method for air-fuel ratio...

2005-04-19

2005-04-19

Lefkowitz, Edward (Department: 2855)

Measuring and testing

Gas analysis

Gas of combustion

Reexamination Certificate

active

06880380

ABSTRACT:
A failure diagnostic apparatus for an air-fuel ratio detecting device has an exhaust emission purifying device provided in an exhaust passage; an air-fuel ratio detecting unit for detecting the air-fuel ratio of an exhaust gas from the purifying device; a first determination unit for determining that the air-fuel ratio is estimated to be rich for longer than a first predetermined period of time; a second determination unit for determining that the air-fuel ratio is estimated to be lean for longer than a second predetermined period of time; and a failure diagnosis device for determining that the air-fuel ratio detecting device has failed if a variation in the air-fuel ratio, calculated based on the detected air-fuel ratios until both the first and second determination units make the determinations, is equal to or less than a predetermined value.

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patent: 4-109445 (1992-09-01), None

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