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Check Open Circuit

Fig 1: Checking Open Circuit
G03693802Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. For an open circuit in the wire harness in Fig 1, perform a resistance check (step  b) or a voltage check (step  c).
  2. Check the resistance.
    Fig 2: Checking Resistance Between Connectors A And C
    G03693803Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect connectors A and C and measure the resistance between them.

      Resistance: Below 1 Ω 

      HINT:

      Measure the resistance while lightly shaking the wire harness vertically and horizontally.

      Fig 2

      TESTER CONNECTION AND SPECIFIED CONDITION

      Tester Connection Specified Condition
      Connector A terminal 1 -Connector C terminal 1 10kΩ or higher
      Connector A terminal 2 -Connector C terminal 2 Below 1 kΩ

      If your results match the examples above, an open circuit exists between terminal 1 of connector A and terminal 1 of connector C.

    2. Disconnect connector B and measure the resistance between the connectors.
      Fig 3: Checking Resistance Between Connectors
      G03693804Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Fig 3:

      CONNECTORS TERMINALS RESISTANCE

      Tester Connection Specified Condition
      Connector A terminal 1 -Connector B1 terminal 1 Below 1 kΩ
      Connector B2 terminal 1 -Connector C terminal 1 10kΩ or higher

      If your results match the examples above, an open circuit exists between terminal 1 of connector B2 and terminal 1 of connector C.

  3. Check the voltage.
    Fig 4: Checking Voltage Between ECU Terminals And Body Ground
    G03693805Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. In a circuit in which voltage is applied to the ECU connector terminal, an open circuit can be checked by conducting a voltage check.

      Fig 4:

      With each connector still connected, measure the voltage between the body ground these terminals (in this order): 1) terminal 1 of connector A at the ECU 5V output terminal, 2) terminal 1 of connector B, and 3) terminal 1 of connector C.

    2. Example results:
      ECU TERMINALS VOLTAGE

      Tester Connection Specified Condition
      Connector A terminal 1 -Body ground 5V
      Connector B terminal 1 -Body ground 5 V
      Connector C terminal 1 -Body ground 0 V

      If your results match the examples above, an open circuit exists in the wire harness between terminal 1 of B and terminal 1 of C.

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