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How To Use The Diagnostic Chart And Inspection Procedure

  1. CONNECTOR CONNECTION AND TERMINAL INSPECTION 
    • For troubleshooting, diagnostic trouble code charts or problem symptom table are provided for each circuit with detailed inspection procedures .
      Fig 1: Checking Connector Connection
      G02843762Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • When all the component parts, wire harnesses and connectors of each circuit except the ECU are found to be normal in troubleshooting, then it is determined that the problem is in the ECU. Accordingly, if diagnosis is performed without the problem symptoms occurring, refer to step  8 to replace the ECU. So always confirm that the problem symptoms are occurring, or proceed with inspection while using the symptom simulation method.
      Fig 2: Checking Wire Harness And Connector
      G02843763Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • The instructions "Check wire harness and connector" and "Check and replace ECU" which appear in the inspection procedure, are common and applicable to all diagnostic trouble codes. Follow the procedure outlined below whenever these instructions appear.

    OPEN CIRCUIT:

    This could be due to a disconnected wire harness, faulty contact in the connector, a connector terminal pulled out, etc.

    NOTE:
    • It is rarely the case that a wire is broken in the middle of it. Most cases occur at the connector. In particular, carefully check the connectors of sensors and actuators
      Fig 3: Identifying Contact Points Of Connectors
      G02843764Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • Faulty contact could be due to rusting of the connector terminals, to foreign materials entering terminals or a deformation of connector terminals. Simply disconnecting and reconnecting the connectors once changes the condition of the connection and may result in a return to normal operation. Therefore, in troubleshooting, if no abnormality is found in the wire harness and connector check, but the problem disappears after the check, then the cause is considered to be in the wire harness or connectors.

    SHORT CIRCUIT:

    This could be due to a contact between wire harness and the body ground or to a short circuit occurred inside the switch, etc.

    NOTE:

    When there is a short circuit between the wire harness and body ground, check thoroughly whether the wire harness is caught in the body or is clamped properly.

  2. CONNECTOR HANDLING 

    When inserting tester probes into a connector, insert them from the rear of the connector. When necessary, use mini test leads. For water resistant connectors which cannot be accessed from behind, take good care not to deform the connector terminals.

    Fig 4: Probing Connectors
    G02843765Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. CONTINUITY CHECK (OPEN CIRCUIT CHECK) 
    1. Disconnect the connectors at both ECU and sensor sides.
      Fig 5: Checking Continuity (Open Circuit Check)
      G02843766Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance between the applicable terminals of the connectors.

      Resistance: 1 Ω or less 

    NOTE:

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

    Fig 6: Preparing Circuits For Resistance Measurement
    G02843767Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  4. RESISTANCE CHECK (SHORT CIRCUIT CHECK) 
    1. Disconnect the connectors on both ends.
      2. NOTE:

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

      Fig 7: Checking Resistance (Short Circuit Check)
      G02843768Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance between the applicable terminals of the connectors and body ground. Be sure to carry out this check on the connectors on both ends.

      Resistance: 1 MΩ or higher 

  5. VISUAL CHECK AND CONTACT PRESSURE CHECK 
      NOTE:

      The terminals should not come out when pulled lightly from the back.

    1. Disconnect the connectors at both ends.
    2. Check for rust or foreign material, etc. in the terminals of the connectors.
      Fig 8: Checking Connectors Using Visual Methods And Contact Pressure
      G02843769Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Check crimped portions for looseness or damage and check that the terminals are secured in lock portion.
      4. CAUTION: When testing a gold-plated female terminal, always use a gold-plated male terminal.
      When the test terminal is pulled out more easily than others, there may be poor contact in that section.
    4. Prepare a test male terminal and insert it in the female terminal, then pull it out.
  6. CHECK OPEN CIRCUIT 

    For the open circuit in the wire harness in Fig 9, perform "(a) Continuity Check" or "(b) Voltage Check" to locate the section.

    Fig 9: Diagramming Circuit
    G02843770Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Check the continuity.
      1. Disconnect connectors "A" and "C" and measure the resistance between them.

        In the case of Fig 10:

        Fig 10: Measuring Circuit Resistance Point A-C
        G02843771Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

        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, it is found out that there is an open circuit between terminal 1 of connector "A" and terminal 1 of connector "C".

      2. Disconnect connector "B" and measure the resistance between the connectors.

        In the case of Fig 11:

        Fig 11: Measuring Circuit Resistance Points A-B1 & B2-C
        G02843772Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

        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, it is found out that there is an open circuit between terminal 1 of connector "B2" and terminal 1 of connector "C".

    2. Check the voltage.

      In a circuit in which voltage is applied (to the ECU connector terminal), an open circuit can be checked for by conducting a voltage check.

      As shown in Fig 12, with each connector still connected, measure the voltage between body ground and terminal 1 of connector "A" at the ECU 5V output terminal, terminal 1 of connector "B", and terminal 1 of connector "C", in that order.

      Fig 12: Locating Short By Checking Circuit Voltage AT Points A, B & C
      G02843773Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      If the results are:

      5V: Between Terminal 1 of connector "A" and Body Ground

      5V: Between Terminal 1 of connector "B" and Body Ground

      0V: Between Terminal 1 of connector "C" and Body Ground

      Then it is found out that there is an open circuit in the wire harness between terminal 1 of "B" and terminal 1 of "C".

  7. CHECK SHORT CIRCUIT 

    If the wire harness is ground shorted as in Fig 13, locate the section by conducting a "continuity check with ground".

    Fig 13: Diagramming Shorted Circuit
    G02843774Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    Check the continuity with ground.

    1. Disconnect connectors "A" and "C" and measure the resistance between terminal 1 and 2 of connector "A" and body ground.

      In the case of Fig 14:

      Fig 14: Locating Side Of Circuit Shorted To Ground
      G02843775Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

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

      Therefore, it is found out that there is a short circuit between terminal 1 of connector "A" and terminal 1 of connector "C".

    2. Disconnect connector "B" and measure the resistance between terminal 1 of connector "A" and body ground, and terminal 1 of connector "B2" and body ground.

      In the case of Fig 15:

      Fig 15: Locating Section Of Circuit Shorted To Ground
      G02843776Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

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

      Therefore, it is found out that there is a short circuit between terminal 1 of connector "B2" and terminal 1 of connector "C".

  8. CHECK AND REPLACE ECU 

    First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty, so replace the ECU with a normal functioning one and check that the symptoms appear.

    1. Measure the resistance between the ECU ground terminal and the body ground.

      Resistance: 1 Ω or less 

      Fig 16: Testing ECU Ground (Connector Connected)
      G02843777Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the ECU connector, check the ground terminals on the ECU side and the wire harness side for bend and check the contact pressure.

    Fig 17: Testing Ground At ECU & ECU Wire Harness Connector (Connector Disconnected)
    G02843778Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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