HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS HOW TO PROCEED WITH TROUBLESHOOTING


  1. OPERATION FLOW

    Tech Tips

    Perform troubleshooting in accordance with the procedures below. The following is an outline of basic troubleshooting procedures. Confirm the troubleshooting procedures for the circuit you are working on before beginning troubleshooting.


    1. VEHICLE BROUGHT TO WORKSHOP


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    2. CUSTOMER PROBLEM ANALYSIS


      1. Ask the customer about the conditions and environment when the problem occurred.


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    3. INSPECT BATTERY VOLTAGE

      Standard voltage
      11 to 14 V

      If the voltage is below 11 V, recharge or replace the battery before proceeding.


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    4. SYMPTOM CONFIRMATION AND DTC (INCLUDING FREEZE FRAME DATA) CHECK


      1. Visually check the wire harnesses, connectors and fuses for open and short circuits.

      2. Warm up the engine to the normal operating temperature.

      3. Confirm the problem symptoms and conditions, and check for DTCs.

        Result
        Result Proceed to
        DTC is output A
        DTC is not output B

        B
        A
    5. DTC CHART


      1. Check the results obtained in the DTC check. Then find the output DTC in the DTC chart. Look at the "Trouble Area" column for a list of potentially malfunctioning circuits and / or parts.


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    6. PROBLEM SYMPTOMS TABLE


      1. Check the results obtained in the symptom confirmation. Then find the problem symptoms in the problem symptoms table. Look at the "Suspected Area" column for a list of potentially malfunctioning circuits and / or parts.


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    7. CIRCUIT INSPECTION OR PARTS INSPECTION


      1. Confirm the malfunctioning circuit or part.


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    8. ADJUST, REPAIR OR REPLACE


      1. Adjust, repair or replace the malfunctioning circuit or parts.


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    9. CONFIRMATION TEST


      1. After the adjustment, repairs or replacement, confirm that the malfunction no longer exists. If the malfunction does not reoccur, perform a confirmation test under the same conditions and in the same environment as when the malfunction occurred the first time.


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  2. CUSTOMER PROBLEM ANALYSIS

    Tech Tips


    • In troubleshooting, confirm that the problem symptoms have been accurately identified. Preconceptions should be discarded in order to make an accurate judgment. To clearly understand what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time the malfunction occurred.

    • Gather as much information as possible for reference. Past problems that seem unrelated may also help in some cases.


    • The following 5 questions are important points in the problem analysis:

      What Vehicle model, system name
      When Date, time, occurrence frequency
      Where Road conditions
      Under what conditions? Running conditions, driving conditions, weather conditions
      How did it happen? Problem symptoms
  3. SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE

    Tech Tips

    The diagnostic system in the LEXUS LS460L / LS460 has various functions.


    • The first function is the Diagnostic Trouble Code (DTC) check. A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs. In a DTC check, a previous malfunction's DTC can be checked by a technician during troubleshooting.


    • Another function is the Input Signal Check, which checks if the signals from various switches are sent to the ECU correctly.

      By using these functions, the problem areas can be narrowed down and troubleshooting is more effective. Diagnostic functions are incorporated in the following systems in the LEXUS LS460L / LS460.

      System

      DTC Check

      (Normal Mode)

      DTC Check

      (Check Mode)

      Freeze Frame Data Sensor Check / Test Mode (Input Signal Check) Data List Active Test Customize Parameter
      SFI System (1UR-FSE) - -
      SFI System (1UR-FE) - -
      Entry and Start System (for 1UR-FE, Start Function) - - -
      Entry and Start System (for 1UR-FSE, Start Function) - - -
      Automatic Transmission System (for AA80E) - -
      Automatic Transmission System (for AA80F) - -
      Air Suspension System - - -
      Tire Pressure Warning System - - -
      Electronically Controlled Brake System - -
      Electric Parking Brake System - - -
      Power Tilt and Power Telescopic Steering Column System - -
      Steering Lock System - - - - -
      Variable Gear Ratio Steering System - -
      Heated Steering Wheel System - - - - -
      Power Steering System - - - -
      Air Conditioning System - - -
      Pre-crash Safety System - - - -
      Airbag System - - - -
      Power Shoulder Belt Anchorage System - - - - -
      Seat Belt Tension Reducer System - - - - - - -
      Seat Belt Warning System - - - - -
      Theft Deterrent System - - -
      Engine Immobiliser System - - - -
      Blocking System - - - - - -
      Cruise Control System - - - -
      Dynamic Radar Cruise Control System - - - -
      Lane-keeping Assist System - - - -
      Lighting System - - -
      Wiper and Washer System - - - - -
      Power Door Lock Control System - - -
      Wireless Door Lock Control System - - -
      Entry and Start System (for Entry Function) - - - -
      Meter / Gauge System - - -
      Audio and Visual System - - - -
      Rear Seat Entertainment System - - - - - -
      Night View System - - - -
      Navigation System - - - -
      G-BOOK System - - - - - -
      LEXUS Parking Assist-sensor System - - -
      Parking Assist Monitor System - - - - -
      Blind Spot Monitor System - - - -
      Electric Power Control System - - - -
      Horn System - - - -
      Clock System - - - - - - -
      Power Window Control System - - -
      Windshield Deicer System - - - - - -
      Window Defogger System - - - - - -
      Power Mirror Control System - - - -
      Front Power Seat Control System - - -
      Rear Power Seat Control System - - -
      Seat Heater System - - -
      Climate Control Seat System - - -
      Door Closer System - - - - - -
      Fuel Lid Opener System - - - - -
      Power Trunk Lid System - - -
      Rear Sunshade System - - -
      Rear Door Sunshade System - - - -
      Sliding Roof System - - -
      LIN Communication System - - - - -
      CAN Communication System (for LHD) - - - - - -
      CAN Communication System (for RHD) - - - - - -

    • In the DTC check, it is very important to determine whether the problem indicated by the DTC is either: 1) still occurring; or 2) occurred in the past but has since returned to normal. In addition, the DTC should be compared to the problem symptom to see if they are related. For this reason, DTCs should be checked before and after confirmation of symptoms (i.e., whether or not problem symptoms exist) to determine current system conditions, as shown in the flowchart below.


    • Never skip the DTC check. Failing to check DTCs may, depending on the case, result in unnecessary troubleshooting for systems operating normally or lead to repairs not related to the problem. Follow the procedures listed in the flowchart in the correct order.


    • The following flowchart shows how to proceed with troubleshooting using the DTC check. Directions from the flowchart will indicate how to proceed either to DTC troubleshooting or to the troubleshooting of each problem symptom.


    1. DTC CHECK


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    2. MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR MEMORY


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    3. SYMPTOM CONFIRMATION

      Result
      Result Proceed to
      No symptoms exist A
      Symptoms exist B

      B
      A
    4. SIMULATION TEST USING SYMPTOM SIMULATION METHODS


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    5. DTC CHECK

      Result
      Result Proceed to
      DTC is not output A
      DTC is output B

      B
      A
    6. SYMPTOM CONFIRMATION

      Result
      Result Proceed to
      Symptoms exist A
      No symptoms exist B

      If a DTC was displayed in the initial DTC check, the problem may have occurred in a wire harness or connector in that circuit in the past. Check the wire harness and connectors.


      B
      A

    The problem is still occurring in a place other than the diagnostic circuit (the DTC displayed first is either for a past problem or a secondary problem).

  4. SYMPTOM SIMULATION

    Tech Tips

    The most difficult case in troubleshooting is when no problem symptoms occur. In such a case, a thorough problem analysis must be carried out. A simulation of the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be carried out. No matter how much skill or experience a technician has, troubleshooting without confirming the problem symptoms will lead to important repairs being overlooked and mistakes or delays.


    1. A01GKF2E01

      VIBRATION METHOD:

      When a malfunction seems to occur as a result of vibration.


      1. PART AND SENSOR

        Apply slight vibration with a finger to the part of the sensor suspected to be the cause of the problem, and check whether or not the malfunction occurs.

        Note

        Applying strong vibration to relays may open them.

      2. CONNECTORS

        Slightly shake the connector vertically and horizontally.

      3. WIRE HARNESS

        Slightly shake the wire harness vertically and horizontally.

        Tech Tips

        The connector joint and fulcrum of the vibration are the major areas that should be checked thoroughly.

    2. HEAT METHOD:

      When a malfunction seems to occur when the area in question is heated.


      1. Heat the component that is the possible cause of the malfunction with a hair dryer or similar device. Check if the malfunction occurs.

        Note


        • Do not heat to more than 60°C (140°F). Exceeding this temperature may damage components.

        • Do not apply heat directly to the parts in the ECU.

    3. A01GNW8

      WATER SPRINKLING METHOD:

      When a malfunction seems to occur on a rainy day or in high-humidity.


      1. Sprinkle water onto the vehicle and check if the malfunction occurs.

        Note


        • Never sprinkle water directly into the engine compartment. Indirectly change the temperature and humidity by spraying water onto the front of the radiator.

        • Never apply water directly onto the electronic components.

        Tech Tips

        If the vehicle has or had a water leakage problem, the leakage may have damaged the ECU or connections. Look for evidence of corrosion or short circuits. Proceed with caution during water tests.

    4. A01GNFQ

      HIGH ELECTRICAL LOAD METHOD:

      When a malfunction seems to occur when the electrical load is excessive.


      1. Turn on the heater blower, headlights, rear window defogger and all other electrical loads. Check if the malfunction reoccurs.

  5. DIAGNOSTIC TROUBLE CODE CHART

    Look for output Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the appropriate section's Diagnostic Trouble Code Chart. Use the chart to determine the trouble area and the proper inspection procedure. A description of each of the chart's columns is below.

  6. Item Description
    DTC Code Indicates the diagnostic trouble code.
    Detection Item Indicates the system or details of the problem.
    Trouble Area Indicates the suspected areas of the problem.
    See Page Indicates where the inspection procedures for each circuit can be found, or where there are instructions for checks and repairs.
  7. PROBLEM SYMPTOMS TABLE

    When a "Normal" code is output during a DTC check but the problem is still occurring, use the Problem Symptoms Table. The suspected areas (circuits or parts) for each problem symptom are in the table. The suspected areas are listed in order of probability. A description of each of the chart's columns is below.

    Tech Tips

    In some cases, the problem is not detected by the diagnostic system even though a problem symptom is present. It is possible that the problem is occurring outside the detection range of the diagnostic system, or that the problem is occurring in a completely different system.

    Item Description
    Symptom -
    Suspected Area Indicates the circuit or part which needs to be checked.
    See Page Indicates where the flowchart for each circuit is located.
  8. CIRCUIT INSPECTION

    A description of the main areas of each circuit inspection is below.

    Item Description
    Circuit Description The major role and operation of the circuit and its component parts are explained.
    DTC Code, DTC Detection Condition, Trouble Area Indicates the diagnostic trouble codes, diagnostic trouble code detection conditions, and trouble areas of a problem.
    Wiring Diagram

    This shows a wiring diagram of the circuit.

    Use this diagram together with an ELECTRICAL WIRING DIAGRAM to thoroughly understand the circuit.

    Inspection Procedures Use the inspection procedures to determine if the circuit is normal or abnormal. If abnormal, use the inspection procedures to determine whether the problem is located in the sensors, actuators, wire harnesses or ECU.
    Inspection Procedure Connector Illustrations
    • Connector being checked is connected:

      Connections of tester are indicated by (+) or (-) after the terminal name.

    • Connector being checked is disconnected:

      For illustrations of inspections between a connector and body ground, information about the body ground is not shown in the illustration.