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Diagnostic apparatus for use in an exhaust system of an internal combustion engine

  • US 5,381,658 A
  • Filed: 11/02/1993
  • Issued: 01/17/1995
  • Est. Priority Date: 11/13/1992
  • Status: Expired due to Fees
First Claim
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1. A diagnostic apparatus for use in an exhaust system of an internal combustion engine, the exhaust system having an exhaust gas passage, a catalyst for purifying the exhaust gas in the exhaust gas passage and an oxygen sensor for detecting an air-fuel ratio in a combustion chamber, wherein a fuel injection volume is controlled for equalizing a primary air-fuel ratio with a predetermined theoretical air-fuel ratio when the engine is operated under normal conditions, and wherein secondary air is supplied to the exhaust gas passage from a secondary air supply mechanism for forcibly adjusting the air-fuel ratio when the engine is operating under extreme conditions, wherein the secondary supply mechanism is composed of a plurality of members, said apparatus comprising:

  • means for computing an actual volume flow rate of the secondary air supplied to the exhaust gas passage from the secondary air supply mechanism;

    means for storing data indicative of the malfunctioning of the secondary air supply mechanism members corresponding to the computed volume flow rate supplied to the exhaust gas passage;

    means for determining which member of the secondary air supply mechanism is malfunctioning based on the value detected by the oxygen sensor and the stored data.

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