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System for diagnosing an internal combustion engine

  • US 4,546,646 A
  • Filed: 09/26/1983
  • Issued: 10/15/1985
  • Est. Priority Date: 10/01/1982
  • Status: Expired due to Fees
First Claim
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1. A system for diagnosing operations of sensing systems of an internal combustion engine comprising:

  • a first diagnosing circuit for diagnosing operation of a first of said sensing systems, said first diagnosing circuit including comparing means for comparing an input from said first sensing system with a reference and said first diagnosing circuit for producing a first output when the input is different than said reference;

    means comprising a display responsive to said first output for indicating trouble in said first sensing system;

    a second diagnosing circuit for diagnosing operation of a second of said sensing systems and for producing a second output when the operation of the second sensing system is abnormal;

    gate means for electrically connecting the second output of said second diagnosing circuit with said display;

    a manually operated terminal for producing a third output when operated; and

    control means responsive to the third output for opening said gate means so as to apply an occurrence of said second output to the display to indicate abnormality of the diagnosing of said second diagnosing circuit.

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