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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). As the resistance may be outside the specifications if measured at high temperatures immediately after the vehicle has been running, measurements should be made when the engine has cooled down.
      Fig 1: Showing Wrong And Right Way Of Handling Of Connector
      G03478869Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. HANDLING OF CONNECTOR
    1. When removing the connector with lock, press the connector in the direction of the engagement and remove the lock by lightly pressing the lock claw.
    2. When removing the connector, do not hold the harness, but hold the connector.
    3. Before connecting the connector, check that there is no deformation, damage or missing terminals.
    4. The connector with a lock should be securely connected until it makes a "click" sound.
    5. When 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 water proof connector cannot be checked from the backside, check by connecting the sub-harness.
    • Do not damage the terminals by moving the inserted tester needle.
  3. CONNECTOR CHECKING POINTS
    1. Checking when the connector is connected:

      By holding the connector, check the inserted condition and locking efficiency (engaged condition).

      Fig 2: Identifying Connector Checking Points
      G03478870Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Checking when the connector is removed:

      Check by lightly pulling the wire harness (missing terminal, terminal crimping condition, core wire break).

      Check visually for is any rust, metal particles, water and bent terminals (rust, mixing of foreign object, terminal deformation).

      NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
    3. Checking of the contact pressure of the terminal:

    Prepare a spare male terminal.

    Insert it into a female terminal, check the engaged condition and sliding resistance.

    Fig 3: Checking Of Contact Pressure Of Terminal
    G03478871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  4. REPAIR METHOD OF CONNECTOR TERMINAL
    1. If there is on the contact point, clean the contact point using an air gun or shop rag. However, never polish the contact point using sand paper as the platings may come off.
    2. In case of abnormal contact pressure, replace the female terminal. However, if a male terminal is gold-plated (gold color), use gold-plated female terminal and if it is silver-plated (silver color), use silver-plated female terminal.
      Fig 4: Showing Wrong And Right Way Of Handling Repair Method Of Connector Terminal
      G03478872Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  5. HANDLING OF WIRE HARNESS
    1. When removing the wire harness, check the positioning of the wiring and clamping before starting work in order to be able to restore it correctly.
    2. Never twist, pull or loosen the wire harness more than necessary.
    3. Never allow the wire harness to come into contact with a high-temperature, rotating, moving, vibrating or sharp (edge of the panel, tip of the screw, etc.) part.
    4. When installing parts, never let the wire harness be interfered with.
    5. Never cut or break the cover of the wire harness. If one is cut or broken, replace it or securely repair it with electrical tape.
      Fig 5: Showing Wrong And Right Way Of Handling Of Wire Harness
      G03478873Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. 2. CHECK OPEN CIRCUIT 
    1. For the open circuit in the wire harness in Fig 6, perform a continuity check in step (b) or a voltage check in step ( c) to locate the Service Category.
      Fig 6: Identifying Open Circuit
      G03478874Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check the continuity.
      1. Disconnect connectors A and C and measure the resistance between them.

        Resistance: 1 Ω or less 

        HINT:

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

        In the case of Fig 7

        Between terminal 1 of connector A and terminal 1 of connector C --> No continuity (open)

        Between terminal 2 of connector A and terminal 2 of connector C --> Continuity

        Therefore, the cause is an open circuit between terminal 1 of connector A and terminal 1 of connector C.

        Fig 7: Checking Continuity
        G03478875Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. Disconnect connector B and measure the resistance between the connectors.

      In the case of Fig 8

      Between terminal 1 of connector A and terminal 1 of connector B1 --> Continuity

      Between terminal 1 of connector B2 and terminal 1 of connector C --> No continuity (open)

      Therefore, the cause is an open circuit between terminal 1 of connector B2 and terminal 1 of connector C.

      Fig 8: Measuring Resistance Between Connectors
      G03478876Courtesy 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.

      As shown in Fig 9with each connector still connected, measure the voltage between the body ground and terminal 1 of connector A at the ECU 5 V output terminal, terminal 1 of connector B, and terminal 1 of connector C, in that order.

    2. If the results are:

      5 V: Between terminal 1 of connector A and body ground

      5 V: Between terminal 1 of connector B and body ground

      0 V: Between terminal 1 of connector C and body ground

      Therefore, the cause is an open circuit in the wire harness between terminal 1 of connector B and terminal 1 of connector C.

      Fig 9: Checking Voltage
      G03478877Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. 3. CHECK SHORT CIRCUIT 
    1. If the wire harness is ground shorted as shown in Fig 10 locate the Service Category by conducting a continuity check with the body ground in step (b).
      Fig 10: Checking Short Circuit
      G03478878Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check the continuity 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.

        In the case of Fig 11

        Between terminal 1 of connector A and body ground --> Continuity (short)

        Between terminal 2 of connector A and body ground --> No continuity

        Therefore, the cause is a short circuit between terminal 1 of connector A and terminal 1 of connector C.

        Fig 11: Checking Continuity With Body Ground
        G03478879Courtesy 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.

        In the case of Fig 12

        Between terminal 1 of connector A and body ground --> No continuity

        Between terminal 1 of connector B2 and body ground --> Continuity (short)

        Therefore, the cause is a short circuit between terminal 1 of connector B2 and terminal 1 of connector C.

        Fig 12: Measuring Resistance Between Terminal Of Connector And Body Ground
        G03478880Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. 4. CHECK AND REPLACE ECU 
    NOTE:
    • Start an inspection of the connector from the backside of the connector on the wire harness side with the connector connected to the ECU.
    • When no measurement condition is specified, perform the inspection with the engine stopped and also the ignition switch ON.
    1. First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. In this case, replace the ECU with one that functions normally and check if the symptoms appear.
    1. Measure the resistance between the ECU ground terminal and body ground.

      Resistance: 1 Ω or less 

      Fig 13: Measuring Resistance Between ECU Ground Terminal And Body Ground
      G03478881Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the ECU connector, check the ground terminals on the ECU side and wire harness side for bends and check the contact pressure.
      Fig 14: Checking Ground Terminals On ECU Side
      G03478882Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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