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Method of determining acceptability of an exhaust concentration sensor

  • US 4,887,576 A
  • Filed: 09/28/1988
  • Issued: 12/19/1989
  • Est. Priority Date: 10/21/1985
  • Status: Expired due to Term
First Claim
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1. A method of determining the acceptability of an exhaust concentration sensor arranged in an exhaust system of an internal combustion engine for sensing the concentration of a component contained in exhaust emitted by the engine, the method comprising the steps of:

  • (1) continuously supplying an air-fuel mixture to the engine at a predetermined constant air-fuel ratio corresponding to a stoichiometric mixture ratio;

    (2) comparing a sensed value outputted by the exhaust concentration sensor indicative of the concentration of said component, with a predetermined reference value;

    (3) obtaining a ratio of a first time period during which the sensed value is higher than said predetermined reference value to a second time period during which said sensed value is lower than said predetermined reference value; and

    (4) determining that the exhaust concentration sensor is acceptable when the obtained ratio between the first time period and the second time period is within a predetermined range, and determining that the exhaust concentration sensor is not acceptable when the obtained ratio between the first time period and the second time period is not within the predetermined range,wherein said exhaust concentration sensor is arranged upstream of a three-way catalyst disposed in said exhaust system, and wherein said predetermined range of said ratio is defined by two extreme limit values, one of which is set to a maximum allowable value of the amount of carbon monoxide and hydrocarbon contained in the exhaust and the other to a maximum allowable value of the amount of nitrogen oxides contained in the exhaust.

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