Method and apparatus for self diagnosis of an internal combustio

Details Method and apparatus for self diagnosis of an internal combustio Method and apparatus for self diagnosis of an internal combustio

1994-09-01

1996-07-09

Hart, Douglas

Power plants

Internal combustion engine with treatment or handling of...

Methods

60276, 60277, 60285, 123688, 123691, F01N 320

Patent

active

055333320

ABSTRACT:
With an air-fuel ratio control apparatus for an internal combustion engine wherein oxygen sensors are respectively arranged upstream and downstream of an exhaust gas purification catalytic converter, air-fuel ratio feedback control is carried out for diagnosis using only the downstream oxygen sensor. When during diagnostic air-fuel ratio feedback control, phase differences of output fluctuations of the two oxygen sensors are below a predetermined value, deterioration of the catalytic converter is judged. A judgment level is variably set based on the results of the deterioration diagnosis of the catalytic converter, and deterioration of response of the downstream oxygen sensor is diagnosed by comparing the output-period of the downstream oxygen sensor with the set judgment level.

REFERENCES:
patent: 5018348 (1991-05-01), Durschmidt
patent: 5154055 (1992-10-01), Nakane
patent: 5220788 (1993-06-01), Kurita
patent: 5331808 (1994-07-01), Koike

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