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Air-fuel ratio detecting apparatus and method

  • US 6,343,499 B1
  • Filed: 11/23/1999
  • Issued: 02/05/2002
  • Est. Priority Date: 12/24/1998
  • Status: Expired due to Term
First Claim
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1. An air-fuel ratio detecting apparatus comprising:

  • an air-fuel ratio sensor having a sensor body which, upon application of a voltage to the sensor body, generates a limit current in accordance with at least one of an oxygen concentration and an unburned gas concentration in a detection-object gas;

    a sensor body drive circuit that drives the sensor body;

    element impedance detection means for detecting an impedance of an oxygen ion-conductive element provided in the sensor body by applying an AC voltage to the sensor body; and

    diagnostic means for detecting and diagnosing faults based on the detected element impedance.

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