Lexus ES: How To Proceed With Troubleshooting

NOTICE:

• Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
• If the CAN communication system is malfunctioning, check the contact pressure of the terminals in connectors, as insufficient terminal contact pressure may be the cause.

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• Before measuring the resistance of the CAN bus, turn the engine switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
• After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

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HINT:

• If the engine switch can be turned to ON (the power source mode can be changed to on) when the vehicle is brought in for repair, check for DTCs and check the illumination condition of the indicators in the combination meter assembly and the basic operation of the vehicle (such as steering operation) promptly.
• Do not turn the engine switch off until the inspection of the vehicle is finished, as some fail-safe functions are canceled when the engine switch is turned off.
• If the engine switch cannot be turned to ON (the power source mode cannot be changed to on) when the vehicle is brought in, measure the voltage of the battery. If the voltage is below 11 V, recharge or replace the battery before performing troubleshooting.
• If the engine switch cannot be turned to ON (the power source mode cannot be changed to on) even though the battery voltage is normal, repair this malfunction before performing troubleshooting.

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HINT:

• 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.
• Ask the customer if the vehicle is/was equipped with additional devices such as a theft deterrent device or monitor. (If equipped, explain to the customer that the additional devices will be removed before performing troubleshooting as the malfunction cannot be checked properly.)
• Examples of points to be confirmed are shown below.

HINT:

• What was affected (system, part or meter warning indicators)
• What happened (details of the malfunction)
• When (occurrence date and time, frequency and if it recurs or not)
• Under what kind of situation did the problem occur (driving and operating condition at the occurrence and weather)
• Road type or condition (city, suburb, paved road, unpaved road, highway, etc.)
• Conditions when vehicle returned to normal (engine switch was turned off, etc.)

HINT:

• It can be determined if the battery is completely drained by operating the horn.
• If the engine switch cannot be turned on (IG), measure the voltage of the battery. If it is below 11 V, perform inspection after replacing or recharging the battery.
• If the engine switch cannot be turned on (IG) even though the battery voltage is normal, repair this malfunction before performing troubleshooting.

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HINT:

• ECUs and sensors are not displayed on the "Communication Bus Check" screen when the Techstream cannot communicate with the vehicle.
• If communication between the Techstream and ECUs is not possible, either the Techstream or vehicle has a malfunction.
• If communication between the Techstream and ECUs is still not possible even when the Techstream is connected to another vehicle, the Techstream has a malfunction. Perform the self tests described in the Techstream operator's manual. (The Techstream may be malfunctioning or its battery may be discharged.)

NOTICE:

• CAN communication DTCs are output when there is an open or short in any of the communication lines. Any problems with the power source of a corresponding ECU or sensor, or problems in the ECU or sensor itself also cause these DTCs to be output.
• If a CAN communication line connector is disconnected with the engine switch on (IG or ACC), the ECUs of the corresponding system and related systems store a DTC.

HINT:

• For details on how to change to and from the "Communication Malfunction Check" screen, refer to Communication Bus Check (Communication Malfunction Check).

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• For the definition of central bus, sub bus and local bus, refer to Definition of Terms.

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• A sub bus monitoring ECU is a gateway function equipped ECU that monitors ECUs and sensors on its respective bus.
• When the vehicle is equipped with a sub bus, refer to System Diagram to confirm the sub bus monitoring ECU.

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• Sub bus monitoring ECUs monitor all ECUs and sensors connected to their respective sub bus and can accurately detect when an ECU or sensor stops communicating.
• When CAN communication DTCs are stored but all ECUs and sensors connected to the CAN communication system are displayed as normal on the "Communication Bus Check" screen of the Techstream, a past malfunction is suspected.
• When a sub bus monitoring ECU detects a communication error in the network, or that an ECU or sensor has stopped communicating, it stores a DTC.
• When CAN communication DTCs are stored in an ECU connected to the central bus and in a sub bus monitoring ECU, inspect the corresponding sub bus and perform repairs if necessary before inspecting the central bus.
• A malfunctioning local bus will not affect the central bus or sub buses.
• When CAN communication DTCs are stored for a local bus, inspect related systems and perform repairs if necessary.

NOTICE:

• A sub bus monitoring ECU outputs DTCs for its respective ECUs and sensors. Identify the malfunctioning ECU or sensor using the output DTCs.
• ECUs or sensors that are not installed to the vehicle will not be displayed. Do not mistake these for ECUs or sensors that are not communicating.
• When using the combo box, it may be possible to select a sub bus from the drop down list that does not have any connected ECUs or sensors. This is not a malfunction and occurs when there is no optional device connected to a sub bus which is monitored by a sub bus monitoring ECU (gateway function equipped ECU).

HINT:

• For details on how to read the "Communication Bus Check" screen, refer to Description of "Communication Bus Check" screen.

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• If there is an ECU or sensor whose connection status changes intermittently while checking the "Communication Bus Check" screen, there may be an open circuit in one of the wires of a branch line of an ECU or sensor in the bus. If an open occurs in one of the wires of a CAN branch line, it may interfere with the communication of other ECUs or sensors resulting in an incorrect state being displayed.
• The central gateway ECU (network gateway ECU) displays the connection status of ECUs and sensors connected to the central bus on the Techstream.
• Sub bus monitoring ECUs display the connection status of ECUs and sensors connected to their respective sub bus on the Techstream.
• If a CAN commutation DTC is output for an ECU connected to the sub bus, refer to the corresponding diagnostic procedure.

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HINT:

• For details on how to inspect buses, refer to How to Use "Communication Bus Check" Screen in Inspection.

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• If there are multiple ECUs or sensors that are not communicating, check for blown fuses before proceeding with troubleshooting.
• If there are multiple ECUs or sensors that are not communicating, after confirming that there are no power supply malfunctions, check for an open in CAN bus main lines, a short in CAN bus lines (CANH or CANL) or a short to ground or +B in CAN bus lines.
• If there is an ECU or sensor that is not communicating, there may be an open circuit in one of the wires of its branch line. In this situation, the malfunctioning wire harness may affect noise immunity and interfere with the communication of other ECUs or sensors on the same bus. This may affect the validity of the displayed data.

HINT:

• For details on the terminal arrangement of the central gateway ECU (network gateway ECU), refer to Terminals of ECU.

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• If the CAN bus main line is normal and there is an ECU or sensor whose connection status changes intermittently while checking the "Communication Bus Check" screen, there may be an open circuit in one of the wires of a branch line of an ECU or sensor in the bus. If an open occurs in one of the wires of a CAN branch line, it may interfere with the communication of other ECUs or sensors resulting in an incorrect state being displayed.

  Performing the bus inspection again may help in determining the suspected area.

NOTICE:

• ECUs or sensors that are not installed to the vehicle will not be displayed. Do not mistake these for ECUs or sensors that are not communicating.
• When using the combo box, it may be possible to select a sub bus from the drop down list that does not have any connected ECUs or sensors. This is not a malfunction and occurs when there is no optional device connected to a sub bus which is monitored by a sub bus monitoring ECU (gateway function equipped ECU).

HINT:

• The communication history of ECUs or sensors which have communication error history can be displayed on the "Communication Bus Check (Detail)" screen.
• Lost Communication Time and Lost Communication Trip are only displayed for the central bus.
• Lost Communication Time and Lost Communication Trip are not displayed for sub buses.

NOTICE:

• ECUs or sensors that are not installed to the vehicle will not be displayed. Do not mistake these for ECUs or sensors that are not communicating.
• When using the combo box, it may be possible to select a sub bus from the drop down list that does not have any connected ECUs or sensors. This is not a malfunction and occurs when there is no optional device connected to a sub bus which is monitored by a sub bus monitoring ECU (gateway function equipped ECU).

HINT:

• For details on "Communication Bus Check (Detail)" screen, refer to How to Use "Communication Bus Check (Detail)" Screen in Inspection.

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• Lost Communication Time and Lost Communication Trip are only displayed for the central bus.
• Lost Communication Time and Lost Communication Trip are not displayed for sub buses.
• If an ECU or sensor has communication stop history, the background color of the ECU or sensor will be red.
• If more than one ECU or sensor has a background color of red, check the values of Lost Communication Trip and Lost Communication Time. Communication error of an ECU or sensor with the value of Lost Communication Trip closest to the Current Trip and the largest value of Lost Communication Time is suspected.

 System Description

 System Diagram

 System Diagram

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