Abnormality diagnosis for air-fuel ratio sensor system

Details Abnormality diagnosis for air-fuel ratio sensor system Abnormality diagnosis for air-fuel ratio sensor system

1998-09-25

2000-10-24

Warden, Sr., Robert J.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204425, 123688, 123690, G01N 27406, F02D 4102

Patent

active

061361690

ABSTRACT:
An air-fuel ratio sensor system is diagnosed for the presence/absence of an abnormality on the basis of a reference voltage appearing at one end of a current detecting resistor and a detection voltage appearing at the other end of the current detecting resistor for detecting a current output by an air-fuel ratio sensor. If the reference voltage is outside a normal range and higher than the detection voltage, the air-fuel ratio sensor system is determined to be in a rich abnormality. If the reference voltage Vafon is outside the normal range and lower than the detection voltage, the air-fuel ratio sensor system is determined to be in a lean abnormality. If the reference voltage is within the normal range and a state of the detection voltage being close to a power supply voltage has been continuing for a predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-shorting. If the reference voltage is within the normal range and a state of the detection voltage being equal to the reference voltage has been continuing at least for the predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-breakage.

REFERENCES:
patent: 4724814 (1988-02-01), Mieno et al.
patent: 4777922 (1988-10-01), Mieno et al.
patent: 5709198 (1998-01-01), Sagisaka et al.
patent: 5833836 (1998-11-01), Takami et al.

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