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HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS HOW TO PROCEED WITH TROUBLESHOOTING

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  1. OPERATION FLOW

    Tip:

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


    1. Click here

      VEHICLE BROUGHT TO WORKSHOP


      • NEXT
    2. Click here

      CUSTOMER PROBLEM ANALYSIS


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


        • NEXT
    3. Click here

      INSPECT BATTERY VOLTAGE

      Standard voltage
      11 to 14 V
      If the voltage is below 11 V, recharge or replace the battery before proceeding.

      • NEXT
    4. Click here

      SYMPTOM CONFIRMATION AND DTC (AND 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
        • GO TO STEP 6
        • A
    5. Click here

      DTC CHART


      1. Check the results obtained in step 4. 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.


        • NEXT
        • GO TO STEP 7
    6. Click here

      PROBLEM SYMPTOMS CHART


      1. Check the results obtained in step 4. 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.


        • NEXT
    7. Click here

      CIRCUIT INSPECTION OR PARTS INSPECTION


      1. Identify the malfunctioning circuit or part.


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    8. Click here

      ADJUST, REPAIR OR REPLACE


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


        • NEXT
    9. Click here

      CONFIRMATION TEST


      1. After the adjustment, repairs or replacement of components, 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 first occurred.


        • NEXT
        • END

  2. CUSTOMER PROBLEM ANALYSIS

    Tip:

    • When 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 items are important points for problem analysis:

      What Vehicle model, system name
      When Date, time, occurrence frequency
      Where Road conditions
      Under what conditions? Driving conditions, weather conditions
      How did it happen? Problem symptoms

  3. SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE

    Tip:

    The diagnostic system in this vehicle 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 can be more effective. Diagnostic functions are incorporated in the following system in this vehicle.

      System Symptom Confirmation and Diagnostic Trouble Code

      DTC Check

      (Normal Mode)

      DTC Check

      (Check Mode)

      		 Sensor Check/Test Mode (Input Signal Check) Data List Active Test
      2GR-FE SFI System ○ ○ - ○ ○
      2AZ-FE SFI System ○ ○ - ○ ○
      Cruise Control System ○ - - ○ ○
      U241E Automatic Transaxle System ○ ○ - ○ ○
      U660E Automatic Transaxle System ○ ○ - ○ ○
      K112 Continuously Variable Transaxle System ○ ○ - ○ ○
      Vehicle Stability Control System ○ - ○ ○ ○
      Power Steering System ○ - - ○ -
      Steering Lock System ○ - - ○ -
      Audio and Visual System ○ - - - -
      Rear Seat Entertainment System ○ - - - -
      Navigation System ○ - - ○ -
      G-BOOK System - - - - -
      Toyota Parking Assist-sensor System ○ - - ○ ○
      Parking Assist Monitor System ○ - - ○ -
      LIN Communication System ○ - - ○ -
      CAN Communication System ○ - - - -
      Power Door Lock Control System ○ - - ○ ○
      Wireless Door Lock Control System ○ - - ○ ○
      Smart Entry and Start System (for Entry Function) - - - ○ ○
      Smart Entry and Start System (for Start Function) ○ - - ○ ○
      Engine Immobiliser System ○ - - ○ ○
      Theft Deterrent System - - - ○ ○
      Lighting System (INT) - - - ○ ○
      Meter / Gauge System ○ - - ○ ○
      Clock System - - - - -
      Airbag System ○ ○ - ○ -
      Front Power Seat Control System (for Driver Side) ○ - - ○ ○
      Front Power Seat Control System (for Front Passenger Side) - - - - -
      Rear Power Seat Control System (w/ Memory) - - - - -
      Rear Power Seat Control System (w/o Memory) - - - - -
      Climate Control Seat System - - - - -
      Seat Heater System - - - - -
      Seat Belt Warning System - - - ○ ○
      Air Conditioning System ○ - - ○ ○
      Power Window Control System ○ - - ○ ○
      Window Defogger System - - - - ○
      Sliding Roof System ○ - - ○ ○
      Power Slide Door System ○ - - ○ ○
      Slide Door Closer System ○ - - ○ -
      Back Door Closer System ○ - - ○ ○
      Power Back Door System ○ - - ○ ○
      Power Mirror Control System (w/ Memory) - - - ○ ○
      Power Mirror Control System (w/o Memory) - - - ○ ○
      Wiper and Washer System - - - - -
      Lighting System (EXT) ○ - - ○ ○
      Horn System - - - - ○

    • In the DTC check, it is very important to determine whether the problem indicated by the DTC either: 1) still occurs, or 2) occurred in the past but has 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, depending on the case, may result in unnecessary troubleshooting for systems operating normally or lead to repairs not related to the problem. Follow the procedure 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. Click here

      DTC CHECK


      • NEXT
    2. Click here

      MAKE A NOTE OF DTC DISPLAYED AND THEN CLEAR MEMORY


      • NEXT
    3. Click here

      SYMPTOM CONFIRMATION

      Result
      Result Proceed to
      No symptoms exist A
      Symptoms exist B

      • B
      • GO TO STEP 5
      • A
    4. Click here

      SIMULATION TEST USING SYMPTOM SIMULATION METHODS


      • NEXT
    5. Click here

      DTC CHECK

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

      • B
      • TROUBLESHOOTING OF PROBLEM INDICATED BY DTC
      • A
    6. Click here

      SYMPTOM CONFIRMATION

      Result
      Result Proceed to
      No symptoms exist A
      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
      • END
      • A
      • TROUBLESHOOTING OF EACH PROBLEM SYMPTOM

    The problem still occurs 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

    Tip:

    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.

    For example
    With a problem that only occurs when the engine is cold or as a result of vibration caused by the road during driving, the problem can never be determined if the symptoms are being checked on a stationary vehicle or a vehicle with a warmed-up engine. Vibration, heat or water penetration (moisture) is difficult to reproduce. The following symptom simulation tests are effective substitutes for the conditions and can be applied to a stationary vehicle. Important points in the symptom simulation test:
    In the symptom simulation test, the problem symptoms as well as the problem area or parts must be confirmed. First, narrow down the possible problem circuits according to the symptoms. Then, connect the tester and carry out the symptom simulation test, judging whether the circuit being tested is defective or normal. Also, confirm the problem symptoms at the same time. Refer to Problem Symptoms Table for each system to narrow down the possible causes.
    To reproduce DTCs, it is necessary to satisfy the respective DTC detection conditions.

    1. A01CAM3E03

      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 the malfunction occurs.

        Note:

        Applying strong vibration to relays may open the relays.

      2. CONNECTORS

        Slightly shake the connector vertically and horizontally.

      3. WIRE HARNESS

        Slightly shake the wire harness vertically and horizontally.

        Tip:

        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 components to more than 60°C (140°F). Exceeding this temperature may damage components.

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

    3. A01CANYE02

      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.

        Tip:

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

    4. A01CAM8

      HIGH ELECTRICAL LOAD METHOD: When a malfunction seems to occur when an electrical load is excessive.


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

  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 shown in the table below.

    Item Description
    DTC No. 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 the page where the inspection procedure for each circuit is to be found, or gives instruction for checking and repairs.

  6. PROBLEM SYMPTOMS TABLE

    When no DTC is output but the problem still occurs, use the Problem Symptoms Table. The suspected areas (circuits or parts) for each problem symptoms are shown in the table. The suspected areas are listed in order of probability. A description of each of the chart columns is shown in the following table.

    Tip:

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

    Item Description
    Problem Symptom -
    Circuit Inspection, Inspection Order Indicates the order in which the circuits need to be checked
    Circuit or Part Name Indicates the circuit or part which needs to be checked
    See page Indicates the page where the flowchart for each circuit is located

  7. CIRCUIT INSPECTION

    A description of the main areas of each circuit inspection is shown in the following table.

    Item Description
    Circuit Description The major role, operation of the circuit and its component parts are explained.
    Diagnostic Trouble Code No. and Detection Item Indicates the diagnostic trouble codes, diagnostic trouble code settings and suspected areas for a problem.
    Wiring Diagram

    This shows a wiring diagram of the circuit.

    Use this diagram together with Electrical Wiring Diagram to thoroughly understand the circuit.

    Wire colors are indicated by an alphabetical code. B = Black, L = Blue, R = Red, BR = Brown, LG = Light Green, V = Violet, G = Green, O = Orange, W = White, GR = Gray, P = Pink, Y = Yellow, SB = Sky Blue

    The first letter indicates the basic wire color and the second letter indicates the color of the stripe.
    Inspection Procedure Use the inspection procedure to determine if the circuit is normal or abnormal. If abnormal, use the inspection procedure to determine whether the problem is located in the sensors, actuators, wire harnesses or ECU.
    Illustration of the ECU connector during the check

    Connector being checked is connected.

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

    Connector being checked is disconnected.

    Inspections between a connector and body ground. Information about body ground is not shown in the illustration.