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Self-diagnosis apparatus for exhaust gas recirculating system

  • US 5,540,091 A
  • Filed: 09/26/1994
  • Issued: 07/30/1996
  • Est. Priority Date: 09/29/1993
  • Status: Expired due to Term
First Claim
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1. A self-diagnosis apparatus for an exhaust gas recirculating system of an internal combustion engine in which exhaust gases are recirculated from an exhaust pipe to an intake pipe through an exhaust gas recirculation passage equipped with an exhaust gas recirculation control means, said apparatus comprising:

  • first means for detecting a change in an intake pressure in said intake pipe and for generating a corresponding output signal;

    second means for detecting a difference between rotational speeds of said engine before and after said exhaust gas recirculation control means opens said exhaust gas recirculation passage; and

    third means for checking a failure of said exhaust gas recirculating system based on an amount of change in the intake pressure detected by said first means only when the difference between said engine rotational speeds detected by said second means is not greater than a predetermined value.

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