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Method of abnormality detection of oxygen concentration sensor

  • US 4,777,922 A
  • Filed: 03/27/1987
  • Issued: 10/18/1988
  • Est. Priority Date: 03/27/1986
  • Status: Expired due to Term
First Claim
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1. A method for controlling an air/fuel ratio of the intake air-fuel mixture of an internal combustion engine provided with an oxygen concentration sensor at the exhaust system thereof, said sensor including a sensor unit having oxygen pump and sensor cell elements forming a gas diffusion central region therebetween into which the exhaust gas is supplied, voltage supply means for supplying a pump voltage determined in accordance with deviation of a sensor voltage appearing across said sensor cell element from a reference voltage so as to maintain said sensor voltage at said reference voltage, and signal generating means for generating an oxygen concentration signal varying with a pump current flowing through said oxygen pump element, said method comprising:

  • setting a target air/fuel ratio in accordance with the load of said engine;

    determining an air/fuel ratio control valve in accordance with the engine operating conditions of said engine while comparing the oxygen concentration signal with said target air/fuel ratio;

    controlling the intake air/fuel ratio in accordance with said air/fuel ratio control value;

    detecting an appearance of a sensor value normally indicative of a rich condition in which the sensed intake air/fuel ratio is withina rich region;

    comparing said sensor voltage with said reference voltage; and

    determining an abnormality of said oxygen concentration sensor according to when said sensor voltage is lower than said reference voltage upon detection of the rich condition in said step of detecting.

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