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Immobilizer for preventing unauthorized starting of a motor vehicle and method for operating the same

  • US 5,675,490 A
  • Filed: 02/20/1996
  • Issued: 10/07/1997
  • Est. Priority Date: 08/20/1993
  • Status: Expired due to Term
First Claim
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1. An immobilizer for a motor vehicle, comprising:

  • a common data line;

    motor vehicle control devices each having an identification code word and each being connected to said common data line; and

    at least one motor vehicle test unit having desired code words identifying said control devices;

    said at least one test unit being connected through said common data line to said control devices;

    said at least one test unit transmitting a request signal, at least during every engine starting operation, through said data line to all of said control devices, causing said control devices to transmit back their identification code words;

    said at least one test unit comparing the identification code words being sent back with the desired code words and determining how many of said control devices reply with a correct identification code word;

    said at least one test unit disabling at least one of said control devices, for preventing starting and driving of the motor vehicle if fewer than a prescribed number of said control devices reply with their identification code word in the event of an interrogation for the identification code words;

    and said at least one test unit enabling all of said control devices if at least the prescribed number of said control devices reply with their identification code word in the event of the interrogation.

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