NETWORKING: CAN COMMUNICATION SYSTEM: DIAGNOSIS SYSTEM; 2018 MY Sienna [11/2017

(a) Systems (ECUs and sensors) that use CAN communication vary depending on the optional settings of the vehicle. Check which systems (ECUs and sensors) are installed on the vehicle.

The ECUs and sensors that are properly connected to the CAN communication system can be displayed using the Techstream.

NOTICE:

It may be possible to select buses that do not have ECUs or sensors from the bus selection pull-down menu. This is not a malfunction. (This occurs when optional devices are not on a sub bus that is monitored by a gateway function equipped ECU.)
In the bus selection pull down menu, all buses applicable to the model are displayed (e.g. LIN communication buses are also displayed). Therefore, refer to the wiring diagrams to check the names of sub buses for CAN communication.
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Different connection statuses are indicated by the background color of ECUs and sensors that are displayed.

Explanation of CAN Bus Check Screen

Gateway function equipped ECUs relay signals between ECUs and sensors connected to different buses.
*1: An ECU or sensor is installed to the vehicle but is not displayed on the "Communication Bus Check" screen.
*2: The gateway function equipped ECU does not memorize ECUs and sensors connected to its respective sub bus.
*3: The gateway function equipped ECU memorizes ECUs and sensors connected to its respective sub bus.
*4: When the central gateway ECU (network gateway ECU) has an internal malfunction or cannot communicate with the Techstream, the name of buses, sub buses, ECUs and sensors will not be displayed.
*5: When no ECUs or sensors are connected to a bus, the message "There is no system found on the communication Bus." will be displayed.
*6: When a gateway function equipped ECU cannot communicate with the central gateway ECU (network gateway ECU), the name of sub buses and ECUs or sensors connected to the sub bus will not be displayed.
*7: When no ECUs or sensors are connected to the sub bus, the message "There is no system found on the communication Bus." will be displayed.
If there is no communication between the Techstream and the vehicle, or no ECUs or sensors are displayed as connected, check the central gateway ECU (network gateway ECU) and V bus (the bus that connects the DLC3 to the central gateway ECU (network gateway ECU)) for malfunctions.

(b) Observe the connection response screen for approximately 2 minutes to check for a change in connection status of the connected ECUs and sensors.

HINT:

If an open occurs in one of the lines of a CAN branch (except DLC3), output from the other branch line (the line that is not open) will be unstable and it may interfere with the response (display) of other ECUs and sensors.
If the connection status changes during the inspection, repair the open in the branch line of the ECU or sensor that does not respond (is not detected) and then perform the CAN bus check again.

(a) When a communication stop is currently occurring, the probable malfunctioning part can be determined from the CAN bus check and by using the following methods.

The following CAN bus wiring diagram is provided only as an example. This wiring diagram is different from the actual wiring diagram for this vehicle.

HINT:

When a communication stop is currently occurring, it is easier to determine the probable malfunctioning part from the CAN bus check rather than from communication DTCs.
Wait for approximately 2 minutes after turning the engine switch on (IG) (or simulate the driving conditions that enable the malfunction to be reproduced) and select "CAN Bus Check". Then observe the communication status of each ECU on the screen.

(b) If a communication error of only 1 ECU or sensor is indicated on the CAN Bus Check screen, a communication stop of the ECU or sensor is suspected.

When there are communication stops, ECUs that are present in the vehicle may not be displayed on the CAN Bus Check screen.

(c) If communication errors for multiple ECUs or sensors are indicated on the CAN Bus Check screen, then a communication stop of the ECU or sensor that shows a more serious communication stop (an ECU or sensor whose background color is red) is suspected.

Explanation of CAN Bus Check Screen

Gateway function equipped ECUs relay signals between ECUs and sensors connected to different buses.
*1: An ECU or sensor is installed to the vehicle but is not displayed on the "Communication Bus Check" screen.
*2: The gateway function equipped ECU does not memorize ECUs and sensors connected to its respective sub bus.
*3: The gateway function equipped ECU memorizes ECUs and sensors connected to its respective sub bus.
*4: When the central gateway ECU (network gateway ECU) has an internal malfunction or cannot communicate with the Techstream, the name of buses, sub buses, ECUs and sensors will not be displayed.
*5: When no ECUs or sensors are connected to a bus, the message "There is no system found on the communication Bus." will be displayed.
*6: When a gateway function equipped ECU cannot communicate with the central gateway ECU (network gateway ECU), the name of sub buses and ECUs or sensors connected to the sub bus will not be displayed.
*7: When no ECUs or sensors are connected to the sub bus, the message "There is no system found on the communication Bus." will be displayed.
The example of the CAN Bus Check screen in the illustration shows the result of electrical noise on the CAN bus which is caused by an open in a CAN branch line of HV is also unstable. In addition, in this example, MB is equipped with a gateway function. Therefore, communication is also unstable between the Sub bus ECUs of MB and the bus 4.
The example in the illustration shows that HV has a red background color on the CAN Bus Check screen. This indicates a more significant communication stop. In this case, a communication stop of HV is suspected.

(d) If a communication error is indicated on both the bus 4 and Sub bus on the CAN Bus Check screen, suspect any communication stop displayed for the bus 4 first.

HINT:

In the CAN bus check, it is possible to confirm the communication status of ECUs connected to the bus after connecting the Techstream to the DLC3. As for sub bus, it is possible to confirm which sub bus connected ECUs can communicate with a gateway function equipped ECU on the bus.
If a gateway function equipped ECU has a communication error, ECUs connected to the gateway function equipped ECU are also affected, and communication stops will be indicated.
The CAN Bus Check screen in the illustration shows that MB has a gateway function and a communication stop in MB is suspected.

(e) If the CAN Bus Check screen indicates a communication stop only in the sub bus, a communication stop in the sub bus is suspected.

HINT:

A communication error in a sub bus does not affect the other buses.
When a gateway function equipped ECU has memorized the ECUs that are connected to the sub bus, if any of the ECUs connected to the gateway function equipped ECU has a communication error, the background color changes to yellow or red. (The displayed name will not disappear.)

(f) If both of the bus 2 main bus lines are open, ECUs or sensors that are located farther away from the central gateway ECU (network gateway ECU) than the open part will be displayed as a communication stop on the CAN Bus Check screen.

If a communication error occurs in an ECU, it is not displayed on the CAN Bus Check screen even though the ECU is present.

(g) If both of the sub bus main bus lines are open, ECUs that are located farther away from the gateway function equipped ECU than the open part will be displayed as a communication stop on the CAN Bus Check screen.

(h) When any of the following malfunctions occur, CAN communication cannot be established and almost all ECUs and sensors on the bus show a communication error on the CAN Bus Check screen.

Details of Malfunction

HINT:

When a malfunction occurs in the bus, almost all ECUs and sensors on the bus and sub bus indicate a communication error (almost all ECUs are not displayed). As communication with the gateway function equipped ECU that is connected to the bus stops, communication from the ECUs connected to the sub bus that is monitored by the gateway function equipped ECU also stops (these ECUs are not displayed).
When a malfunction occurs in a sub bus, almost all ECUs connected to the sub bus indicate a communication error.
A communication error in a sub bus does not affect the other buses.
The malfunctioning part can be determined by checking for a short circuit between CAN bus lines or between a CAN bus line and ground or +B short using an electrical tester.

(i) If a communication error of all ECUs and sensors is indicated on the CAN Bus Check screen, a communication stop of the V bus (DLC3 - central gateway ECU (network gateway ECU)) is suspected.

When there is no communication between the Techstream and the vehicle, no ECUs or sensors will be displayed.

HINT:

In the CAN communication system, CAN communication system DTCs stored by the ECU can be output by using the Techstream.
If CAN communication system DTCs are output, the trouble cannot be determined solely from the DTCs. Perform troubleshooting according to "How to Proceed with Troubleshooting".

(i) OUTER MIRROR CONTROL ECU ASSEMBLY LH AND OUTER MIRROR CONTROL ECU ASSEMBLY RH

The airbag sensor assembly is connected to the CAN communication system but CAN communication DTCs are not stored.

The front power seat switch LH is connected to the CAN communication system but CAN communication DTCs are not stored.

The central gateway ECU (network gateway ECU) is connected to the CAN communication system, but the central gateway ECU (network gateway ECU) does not store or output CAN communication DTCs.

The steering angle sensor (spiral cable with sensor sub-assembly) is connected to CAN communication system but CAN communication DTCs are not stored.

The power back door unit assembly (back door ECU) is connected to CAN communication system but CAN communication DTCs are not stored.

The slide door motor unit is connected to CAN communication system but CAN communication DTCs are not stored.

The millimeter wave radar sensor assembly is connected to the CAN communication system, but the millimeter wave radar sensor assembly does not store or output CAN communication DTCs.

HINT:

The following waveforms are measured between terminals CANH and GND, and terminals CANL and GND of the central gateway ECU (network gateway ECU). (Use this as a reference for diagnosis of CAN communication lines.)
When malfunctions in multiple ECUs are suspected based on the CAN bus check and DTCs checked using the Techstream, check the resistance of the CAN bus using an ohmmeter first. If no problems are found, check the following waveforms.
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If a waveform is not similar to one of the following 3 patterns (Group 1), then an open in a CAN main bus line, an open in a CAN branch line, or a short between a CAN line (CANH or CANL) and ground is suspected (Group 2).
Wiggle the connector and wire harness to check if the waveform changes.

HINT:

Waveforms (waveforms shown using dotted lines) are not present from an ECU or sensor connected to a CAN branch with an open circuit in both lines. (Waveforms from other ECUs or sensors are normal.)
Because this waveform is similar to a normal waveform, instead of using the waveform, the malfunctioning part can be narrowed down by performing a CAN bus check.

The following CAN bus waveforms can be used only as reference. The actual measured waveform may differ significantly depending on the location of the open or short circuit.

HINT:

An abnormal waveform is output from an ECU with an open in one of its CAN branch lines. Because this abnormal output interferes with the signals from other ECUs, the output of other ECUs will also appear abnormal.
Narrow down the malfunctioning part by checking DTCs or performing a CAN bus check, or by checking waveform changes when ECUs or sensors are disconnected. The waveform will change to one for an open in both sides of a CAN branch when the ECU or sensor with an open CAN branch line is disconnected.

HINT:

An abnormal waveform is output from an ECU with an open in one of its CAN branch lines. Because this abnormal output interferes with the signals from other ECUs, the output of other ECUs will also appear abnormal.
Narrow down the malfunctioning part by checking DTCs or performing a CAN bus check, or by checking waveform changes when ECUs or sensors are disconnected. The waveform will change to one for an open in both sides of a CAN branch when the ECU or sensor with an open CAN branch line is disconnected.

HINT:

Waveforms of ECUs or sensors that are closer to the DLC3 than the open part are almost normal.
Waveforms of ECUs or sensors that are on the opposite side of the DLC3 from the open part are abnormal.
An open in a CAN main bus line can be confirmed by measuring the resistance between the CANH and CANL terminals of any CAN branch.

HINT:

Narrow down the shorted part by checking for waveform changes when disconnecting connectors from the CAN junction connectors or when disconnecting ECUs or sensors.
A short to ground in the CANH line can be confirmed by measuring the resistance between CANH and ground using an ohmmeter.

HINT:

Narrow down the shorted part by checking for waveform changes when disconnecting connectors from the CAN junction connectors or when disconnecting ECUs or sensors.
A short to ground in the CANL line can be confirmed by measuring the resistance between CANL and ground using an ohmmeter.