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Electronic Circuit Inspection Procedure

WARNING: This page is about a different car, the 2004 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
  1. BASIC INSPECTION 
    1. RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS
      1. Unless stated, all resistance is measured at an ambient temperature of 20°C (68°F). Resistances measured may be outside the specifications if measured at high temperatures, i.e. immediately after the vehicle has been running. Measurements should be made after the engine has cooled down.
      Fig 1: Connector Disconnecting Method
      G02916896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. HANDLING CONNECTORS
    1. When disconnecting a connector, first squeeze the mating halves tightly together to release the lock, then press the lock claw and separate the connector.
    2. When disconnecting a connector, do not pull on the harnesses. Grasp the connector directly and separate it.
    3. Before connecting the connector, check that there are no deformed, damaged, loose or missing terminals.
    4. When connecting a connector, press firmly until you hear the lock close with a "click" sound.
    5. If checking the connector with a TOYOTA electrical tester, check it from the backside (harness side) of the connector using a mini test lead.
    NOTE:
    • As a waterproof connector cannot be checked from the backside, check by connecting a sub-harness.
    • Do not damage the terminals by moving the inserted tester needle.
    Fig 2: Checking Looseness Of Crimping
    G02916897Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. CHECKING CONNECTORS
    1. Checking when the connector is connected:

      Squeeze the connector together to confirm that it is fully inserted and locked.

    2. Checking when the connector is disconnected:

      Check by pulling the wire harness lightly from the backside of the connector. Look for unlatched terminals, missing terminals, loose crimps or broken conductor wires.

      Check visually for corrosion, metallic or foreign objects and water; and bent, rusted, overheated, contaminated, and deformed terminals.

      NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
      Fig 3: Checking Contact Pressure Of Terminal
      G02916898Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Checking the contact pressure of the terminal:

      Prepare a spare male terminal. Insert it into a female terminal, and check for good tension when inserting and after full engagement.

      Fig 4: Repairing Method Of Connector Terminal
      G02916899Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. REPAIR METHOD OF CONNECTOR TERMINAL
    1. If there is any dirt on the terminal, clean the contact point using an air gun or shop rag. Never polish the contact point using sandpaper as the platings may come off.
    2. If there is abnormal contact pressure, replace the female terminal. If the male terminal is gold-plated (gold color), use a gold-plated female terminal; if it is silver-plated (silver color), use a silver-plated female terminal.
    3. Damaged, deformed, or corroded terminals should be replaced. If the terminal will not lock into the housing, the housing may have to be replaced.
    Fig 5: Locating Wire Harness
    G02916900Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  4. HANDLING OF WIRE HARNESS
  1. If removing a wire harness, check the wiring and clamping before proceeding so that it can be restored in the same way.
  2. Never twist, pull or slacken the wire harness more than necessary.
  3. Never make the wire harness come into contact with a high temperature part, rotating, moving, vibrating or sharp-edged parts. Avoid panel edges, screw tips and similar sharp items.
  4. When installing parts, never pinch the wire harness.
  5. Never cut or break the cover of the wire harness. If it is cut or broken, replace it or securely repair it with vinyl tape.
    Fig 6: Checking Resistance Open Circuit
    G02916901Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  6. CHECK OPEN CIRCUIT 
    1. For an open circuit in the wire harness in Fig. 1, perform a resistance check (step  b) or a voltage check (step  c).
      Fig 7: Checking Resistance Between A And C Connectors
      G02916902Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check the resistance.
      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:

        OPEN CIRCUIT TERMINAL RESISTANCE

        Tester Connection Specified Condition
        Connector A terminal 1 - Connector C terminal 1 10 kΩ 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.

        Fig 8: Checking Resistance Connector B
        G02916903Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. Disconnect connector B and measure the resistance between the connectors.

        Fig. 3:

        RESISTANCE TESTING

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

        Fig 9: Checking Voltage
        G02916904Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Check the voltage.
    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:
      VOLTAGE SPECIFICATION OPEN CIRCUIT

      Tester Connection Specified Condition
      Connector A terminal 1 - Body ground 5 V
      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.

      Fig 10: Checking Resistance - Short Circuit With Body Ground
      G02916905Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. CHECK SHORT CIRCUIT 
      1. If the wire harness is ground shorted (Fig. 5), locate the section by conducting a resistance check with the body ground (below).
        Fig 11: Checking Resistance Between Terminal 1 And 2
        G02916906Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. Check the resistance with the body ground.
      1. Disconnect connectors A and C and measure the resistance between terminals 1 and 2 of connector A and the body ground.

        Resistance: 10 kΩ or higher 

        HINT:

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

        Fig. 6:

        SHORT CIRCUIT RESISTANCE TESTING DISCONNECTOR A AND C

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

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

        Fig 12: Checking Resistance Between Terminal 1 Of Connector A And Body Ground
        G02916907Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. Disconnect connector B and measure the resistance between terminal 1 of connector A and the body ground, and terminal 1 of connector B2 and the body ground.

        Fig. 7:

        SHORT CIRCUIT RESISTANCE TESTING DISCONNECTOR B

        Tester Connection Specified Condition
        Connector A terminal 1 - Body ground 10 kΩ or higher
        Connector B2 terminal 1 - Body ground Below 1 kΩ

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

      3. CHECK AND REPLACE ECU 
        NOTE:
        • The connector should not be disconnected from the ECU. Perform the inspection from the backside of the connector on the wire harness side.
        • When no measuring condition is specified, perform the inspection with the engine stopped and the ignition switch ON.
        • Check that the connectors are fully seated. Check for loose, corroded or broken wires.
        1. First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. Replace the ECU with a normal functioning one and check if the symptoms occur. If the trouble symptoms stop, replace the ECU.
          Fig 13: Checking Resistance ECU Ground Terminal And Body Ground
          G02916908Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
          1. Measure the resistance between the ECU ground terminal and body ground.

            Resistance: Below 1 Ω 

            Fig 14: Disconnecting ECU Connector
            G02916909Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
          2. Disconnect the ECU connector. Check the ground terminals (on the ECU side and wire harness side) for evidence of bending, corrosion or foreign material. Lastly check the contact pressure of the female terminals.
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