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Diagnostic system for a cooling water temperature sensor

  • US 5,884,243 A
  • Filed: 06/20/1997
  • Issued: 03/16/1999
  • Est. Priority Date: 06/24/1996
  • Status: Expired due to Term
First Claim
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1. A diagnostic system, for determining whether a cooling water temperature sensor for detecting a cooling water temperature of an internal combustion engine has failed, comprising:

  • a parameter detecting means for detecting an engine operating parameter which represents the engine operating conditions affecting a warming up of the engine;

    increment value setting means for setting an increment value based on said engine operating parameter;

    count means for increasing a warming up counter, which represents degree of warming up of the engine, by said increment value at predetermined intervals;

    comparing means for comparing a cooling water temperature detected by a cooling water temperature sensor and a predetermined reference value when the value of said warming up counter reaches a predetermined setting value; and

    determining means for determining that the cooling water temperature sensor has failed when the detected cooling water temperature is lower than said predetermined reference value.

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