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Apparatus for diagnosing automatic transmission based on engine speed as compared with reference range

  • US 5,515,272 A
  • Filed: 12/20/1994
  • Issued: 05/07/1996
  • Est. Priority Date: 12/22/1993
  • Status: Expired due to Term
First Claim
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1. A diagnosing apparatus for detecting a defect associated with an automatic transmission system of a motor vehicle, said automatic transmission system including (a) an automatic transmission having a plurality of operating positions, operatively connected to an engine of the vehicle through a fluid-actuated power transmitting device, and incorporating a plurality of frictional coupling devices for establishing said operating positions, (b) a plurality of solenoid-operated valves for controlling operating states of said frictional coupling devices according to shift commands, and (c) an electronic control device which generates the shift commands to place said automatic transmission in a selected one of said plurality of operating positions, depending upon a running condition of the vehicle, said diagnosing apparatus comprising:

  • engine speed detecting means for detecting a speed of said engine;

    range determining means for determining a reference range of the speed of the engine within which the speed of the engine is expected to fall when said automatic transmission is placed in one of said operating positions which is selected by a shift command generated by said electronic control device;

    condition determining means for determining whether said vehicle is placed in a predetermined running condition; and

    defect detecting means for determining whether there exists a defect associated with said automatic transmission system, depending upon whether the speed of the engine detected by said engine speed detecting means is held within or outside said reference range when said condition determining means determines that said vehicle is placed in said predetermined running condition.

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