CAN COMMUNICATION SYSTEM DIAGNOSIS SYSTEM

ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM
1. V Bus
  1. ECM
  2. Brake booster with master cylinder assembly (Skid control ECU)
  3. Main body ECU (Multiplex network body ECU)
  4. Air conditioning amplifier assembly
  5. Power steering ECU assembly
  6. Smart key ECU assembly (Certification ECU)
  7. Airbag sensor assembly
  8. Steering sensor
  9. Clearance warning ECU assembly*4
  10. Power management control ECU
  11. Combination meter assembly
  12. Navigation ECU sub-assembly*1*2
  13. Radio and display receiver assembly*3
2. Sub Bus 11*5
  1. Power management control ECU
  2. Blind spot monitor sensor RH
3. Sub Bus 15
  1. ECM
  2. Power management control ECU
  3. Brake booster with master cylinder assembly (Skid control ECU)
    Tech Tips
    - *1: for Navigation receiver type
    - *2: for Radio and display type (w/ Intuitive parking assist system)
    - *3: for Radio and display type (w/o Intuitive parking assist system)
    - *4: w/ Intuitive parking assist system
    - *5: w/ Blind spot monitor system

CHECK FOR INSTALLED SYSTEMS (ECUS AND SENSORS) THAT ADOPT CAN COMMUNICATION

The systems (ECUs and sensors) that adopt CAN communication vary depending on the vehicle and optional equipment. Check which systems (ECUs and sensors) are installed on the vehicle.

Tech Tips

The names of ECUs and sensors shown on the Techstream display may differ from those shown in the DTC Table by ECU section that follows.

ECU/Sensor Name	Techstream Display	Applicability
ECM	ECM (Engine)	Installed on all vehicles
Multiplex network body ECU	Main Body	Installed on all vehicles
Brake booster with master cylinder assembly (Skid control ECU)	Skid Control (ABS/VSC/TRAC)	Installed on all vehicles
Radio and display receiver assembly	Display and Navigation (AVN1)	Vehicles with radio and display receiver assembly (w/o intuitive parking assist system)
Navigation ECU sub-assembly	Display and Navigation (AVN1)	Vehicles with navigation receiver assembly Vehicles with radio and display receiver assembly (w/ intuitive parking assist system)
Power steering ECU assembly	Power Steering (EPS)	Installed on all vehicles
Air conditioning amplifier assembly	Air Conditioning Amplifier	Installed on all vehicles
Airbag sensor assembly	Airbag	Installed on all vehicles
Smart key ECU assembly (Certification ECU)	Certification (Smart)	Installed on all vehicles
Clearance warning ECU assembly	Clearance warning (Intuitive Parking Assist2)	Vehicles with intuitive parking assist system
Power management control ECU	Hybrid Vehicle Control Power management1	Installed on all vehicles
Steering sensor	Spiral cable (Steering Angle Sensor)	Installed on all vehicles
Combination meter assembly	Combination Meter	Installed on all vehicles
Blind spot monitor sensor RH	Blind Spot Monitor Master	Vehicles with blind spot monitor system

CAN BUS CHECK

Tech Tips

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

Using the Techstream, select "CAN Bus Check" from "System Select".

Note

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 Click here.

Tech Tips

Different connection statuses are indicated by the background color of ECUs and sensors that are displayed.

Explanation of CAN Bus Check (Communication Bus Check) screen
Bus Type	Background Color	Connection Status
V Bus	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring (unstable communication).
	Not displayed	Communication stop has continued since the start of the CAN bus check.*1
Sub bus (gateway function equipped ECU that does not have history of connected ECUs)*2	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring (unstable communication).
	Not displayed	Communication stop has continued since the start of the CAN bus check.*1
Sub bus (gateway function equipped ECU that has history of connected ECUs)*3	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Currently not communicating (either of the following): Communication stop has continued since the start of the CAN bus check Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring
	Not displayed	Either of the following: If a gateway function equipped ECU cannot communicate, the sub bus and ECUs connected to the sub bus will not be displayed. If no ECUs are connected to the sub bus, "There is no system found on the Communication Bus" will be displayed.

Tech Tips

Gateway function equipped ECUs relay signals between the ECUs connected to the different buses.
*1: ECUs that are present in the vehicle but are not displayed on CAN Bus Check.
*2: Gateway function equipped ECU that does not memorize the sub bus ECUs that are connected to it.
*3: Gateway function equipped ECU that memorizes the sub bus ECUs that are connected to it.
If none of the connected ECUs are displayed, or there is no response from the vehicle to the Techstream, check the DLC3 branch and the V bus main bus lines for a malfunction.

Observe the connection response screen for approximately 2 minutes to check for a change in connection status of the connected ECUs and sensors.
Tech Tips
- 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 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.

HOW TO INTERPRET CAN BUS CHECK (COMMUNICATION BUS CHECK) SCREEN

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.

Note

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.
Tech Tips
- 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 power switch on (IG) (or simulate the driving conditions that enable the malfunction to be reproduced) and select the CAN bus check. Then observe the communication status of each ECU on the screen.

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.

Example: Open in both CAN branch lines of ECU B on the V bus

Text in Illustration
*a	V Bus	*b	Sub Bus
*c	Terminating Resistor	*d	Location of Malfunction
*e	Not displayed or background color changes to red or yellow	*f	CAN Bus Check Screen

Tech Tips

When there are communication stops, ECUs are present in the vehicle even though they are not displayed on the CAN Bus Check screen.

Text in Illustration
*a	Background color periodically changes to yellow or red
*b	Not displayed or background color is yellow or red
*c	Not displayed

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 a sensor which is not displayed) is suspected.

Example: Open in a CAN branch line for ECU D on the V bus

Explanation of CAN Bus Check (Communication Bus Check) screen
Bus Type	Background Color	Connection Status
V Bus	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring (unstable communication).
	Not displayed	Communication stop has continued since the start of the CAN bus check.*1
Sub bus (gateway function equipped ECU that does not have history of connected ECUs)*2	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring (unstable communication).
	Not displayed	Communication stop has continued since the start of the CAN bus check.*1
Sub bus (gateway function equipped ECU that has history of connected ECUs)*3	White	Communication has been normal since the start of the CAN bus check.
	Yellow	Communication stop occurred at least once since the start of the CAN bus check, but communication is currently occurring (unstable communication).
	Red	Currently not communicating (either of the following): Communication stop has continued since the start of the CAN bus check Communication was established at least once since the start of the CAN bus check, but communication is currently not occurring
	Not displayed	Either of the following: If a gateway function equipped ECU cannot communicate, sub bus and ECUs connected to the sub bus will not be displayed. If no ECUs are connected to the sub bus, "There is no system found on the Communication Bus" will be displayed.

Tech Tips

Gateway function equipped ECUs relay signals between the ECUs connected to the different buses.
*1: ECUs that are present in the vehicle but are not displayed on the CAN Bus Check screen.
*2: Gateway function equipped ECU that does not memorize the sub bus ECUs that are connected to it.
*3: Gateway function equipped ECU that memorizes the sub bus ECUs that are connected to it.
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 ECU D (output from the other branch line is unstable) and the communication of ECU C is also unstable. In addition, in this example, ECU C is equipped with a gateway function. Therefore, communication is also unstable between the sub bus ECUs of ECU C and the V bus.
The example in the illustration shows that ECU D is not displayed on the CAN Bus Check screen. This indicates a more significant communication stop. In this case, a communication stop of ECU D is suspected.

Text in Illustration

*a Not displayed or background color changes to red

If a communication error is indicated on both the V bus and sub bus on the CAN Bus Check screen, suspect any communication stop displayed for the V bus first.

Example: Open in both CAN branch lines of ECU C on the V bus
Tech Tips
- In the CAN bus check, it is possible to confirm the communication status of ECUs connected to the V bus after connecting the Techstream to the DLC3. As for sub buses, it is possible to confirm which sub bus connected ECUs can communicate with a gateway function equipped ECU on the V 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 ECU C has a gateway function and a communication stop in ECU C is suspected.
Text in Illustration

*a Background color changes to red

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

Example: Open in both CAN branch lines of ECU G on the sub bus
Tech Tips
- A communication error in a sub bus does not affect the V bus or 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.)

Text in Illustration
*a	Not displayed or background color changes to red

Text in Illustration
*a	Background color changes to red

If both of the V bus main bus lines are open, ECUs or sensors that are located farther away from the DLC3 than the open part will be displayed as a communication stop on the CAN Bus Check screen.

(In this case, ECU A and B are not displayed or their background color changes to red.)

Text in Illustration
*a	V Bus	*b	Sub Bus
*c	Terminating Resistor	*d	Location of Malfunction
*e	Not displayed or background color is red	*f	CAN Bus Check Screen

Tech Tips

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

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.

(In this case, ECU I and J are not displayed or their background color changes to red.)

Text in Illustration
*a	V Bus	*b	Sub Bus
*c	Terminating Resistor	*d	Location of Malfunction
*e	Not displayed or background color is red	*f	CAN Bus Check Screen
*g	Gateway Function Equipped ECU	-	-

Text in Illustration
*a	When any of the following malfunctions occur on the V bus
*b	When any of the following malfunctions occur on a sub bus
*c	Not displayed

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
Short between CAN lines (CANH and CANL)
Short between a CAN line (CANH or CANL) and +B
Short between a CAN line (CANH or CANL) and ground
Open in a CAN main bus line

Tech Tips

When a malfunction occurs on the V bus, almost all ECUs and sensors on the V 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 V 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 V bus or 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.

HOW TO INTERPRET COMMUNICATION DTCS (DTCS THAT START WITH U)

If a CAN communication error cannot be reproduced, determine the suspected malfunctioning part using the DTCs stored in ECUs that are connected to the CAN buses by following the procedure below.

Tech Tips

Communication DTCs (DTCs that start with U) indicate a communication error between the ECU that stores the DTC and the ECU that is indicated by the DTC.
1. If multiple ECUs store a communication DTC for a particular ECU, a communication stop of the ECU is suspected.
  
  Text in Illustration
  
  *a Items to be Checked - -
  Note
  
  This DTC table is from another model, and is only used here to show an example of DTCs that are output when there is an open in a CAN branch line for the main body ECU. This table does not show DTCs applicable to this vehicle.
  
  Even though a DTC title may indicate a communication error with a specific ECU, the ECU name used in the DTC name on the Techstream may differ depending on the ECU that stores the DTC. (Regarding output DTCs, refer to step 6 and the DTC chart for each ECU.)
  Tech Tips
  
  As multiple ECUs indicate a communication stop with the main body ECU, the possibility of a communication stop of the main body ECU is high.
2. If almost all of the communication DTCs of an ECU are stored, a communication stop of the ECU is suspected.
  
  Text in Illustration
  
  *a Items to be Checked - -
  
  Note
  
  This DTC table is from another model, and is only used here to show an example of DTCs that are output when there is an open in a CAN branch line for the main body ECU. This table does not show DTCs applicable to this vehicle.
  
  Tech Tips
  
  If almost all of the DTCs of the main body ECU are stored, the possibility of a communication stop of the main body ECU is high.
3. When a CAN communication error occurs, many DTCs are output. DTCs other than communication error DTCs (such as DTCs that start with C or B) and communication DTCs for the ABS system are important DTCs, however it may be easier to determine the malfunctioning part by examining the overall situation without considering these DTCs.

Text in Illustration
*a	Items to be Checked	-	-

Text in Illustration
*a	Items to be Checked	-	-

To help determine the part of the sub bus that has a communication error, prioritize the communication stop DTCs stored in the gateway function equipped ECU.

Text in Illustration
*a	Items to be Checked	*b	ECM
*c	Gateway Function Equipped ECU	*d	Location of Malfunction
*e	V Bus	*f	Sub Bus

Note

This DTC table is from another model, and is only used here to show the ECUs connected to both a V bus and a sub bus. It shows DTCs output when there is an open in the main bus lines for the ECM on the sub bus. This table does not show DTCs applicable to this vehicle.

Tech Tips

As gateway function equipped ECUs (sub bus monitor ECU) monitor signals from all ECUs that are connected to sub buses, gateway function equipped ECUs can detect ECUs with a communication stop more accurately.
When there is a communication stop for the gateway function equipped ECU (gateway), communication with ECUs connected to other buses such as the V bus stops. Therefore, communication DTCs for ECUs connected to other buses are also stored.

When any of the following malfunctions occurs, many DTCs are likely to be output from many ECUs. Because of this, it may be difficult to determine the probable malfunctioning part.
- Short between CAN lines (CANH and CANL)
- Short between a CAN line (CANH or CANL) and ground
- Short between a CAN line (CANH or CANL) and +B
- Open in a CAN branch line (CANH or CANL) of an ECU or sensor
- Open in a CAN main bus line (CANH or CANL) between 2 ECUs that have a terminating resistor

DTC TABLE BY ECU

Note

If system function temporarily returns to normal, DTCs may not be output again even though the following DTC check procedures are used.

Tech Tips

In the CAN communication system, the CAN communication DTCs of each ECU can be displayed using the Techstream.
If CAN communication system DTCs are output, the malfunction cannot be determined only by the DTCs. Perform troubleshooting according to How to Proceed with Troubleshooting Click here.

Power Management Control ECU / Techstream Display "Hybrid Control"

Tech Tips

This ECU uses the CAN communication system for DTC communication.
*1: Refer to Hybrid Control System Click here.
*2: Refer to Hybrid Battery System Click here.

Power Management Control ECU / Techstream Display "Hybrid Control"
DTC	Detection Item	DTC Detection Condition	DTC Detection Pre-condition	DTC Check Procedure	Warning Indication in Meter	DTC Storage Method
U0100	Lost Communication with ECM / PCM "A"	The power management control ECU (HV CPU) does not receive data from the ECM for 0.58 seconds or more.	Both conditions are met: The power switch is on (IG) for 1 second or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 1.58 seconds.	Master warning light illuminates. MIL illuminates.	DTC is stored until it is cleared using the Techstream.
U0110*1	Lost Communication with Drive Motor Control Module "A"	Either condition is met: The power management control ECU (HV CPU) does not receive data from the inverter with converter assembly (MG ECU) for 0.11 seconds or more. The power management control ECU (HV CPU) does not send data to the inverter with converter assembly (MG ECU) for 0.04 seconds or more.	Both conditions are met: The power switch is on (IG) for 0.1 seconds or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 0.21 seconds.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.
U0129	Lost Communication with Brake System Control Module	The power management control ECU (HV CPU) does not receive data from the brake booster with master cylinder assembly (skid control ECU) for 2.34 seconds or more.	Both conditions are met: The power switch is on (IG) for 2.1 seconds or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 4.44 seconds.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.
U0140	Communication Error from Body ECU to HV ECU	The power management control ECU (HV CPU) does not receive data from the multiplex network body ECU for 3.6 seconds or more.	Both conditions are met: The power switch is on (IG) for 1 second or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 4.6 seconds.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.
U0151	Communication Error from Airbag ECU to HV ECU	The power management control ECU (HV CPU) does not receive data from the airbag sensor assembly for 10.6 seconds or more.	Both conditions are met: The power switch is on (IG) for 1 second or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 11.6 seconds.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.
U0164	Communication Error from A/C ECU to HV ECU	The power management control ECU (HV CPU) does not receive data from the air conditioning amplifier assembly for 10.6 seconds or more.	Both conditions are met: The power switch is on (IG) for 1 second or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 11.6 seconds.	-	DTC is stored until it is cleared using the Techstream.
U029A*2	Lost Communication with Hybrid Battery Pack Sensor Module	The power management control ECU (HV CPU) does not receive data from the battery smart unit for 0.5 seconds or more.	The power switch is on (IG) for 0.5 seconds or more.	Turn the power switch on (IG) and wait at least 1 second.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.
U0424*1	Invalid Data Received from HVAC Control Module	The power management control ECU (HV CPU) receives an abnormal operation value command from the air conditioning amplifier assembly for 3 seconds or more.	Both conditions are met: The power switch is on (IG) for 0.5 seconds or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 3.5 seconds.	-	DTC is stored until it is cleared using the Techstream.
U1107	Lost Communication with Power Management Module	The power management control ECU (HV CPU) does not receive data from the power management control ECU (power management CPU) for 3.6 seconds or more.	Both conditions are met: The power switch is on (IG) for 1 second or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 4.6 seconds.	Master warning light illuminates.	DTC is stored until it is cleared using the Techstream.

Power Management Control ECU / Techstream Display "Power Source Control"

Tech Tips

This ECU uses the CAN communication system for DTC communication.
*1: Refer to Smart Key System (for Start Function) Click here.

Power Management Control ECU / Techstream Display "Power Source Control"
DTC	Detection Item	DTC Detection Condition	DTC Detection Pre-condition	DTC Check Procedure	Warning Indication in Meter	DTC Storage Method
U0140	Lost Communication with Main Body ECU	The power management control ECU (power management CPU) does not receive data from the multiplex network body ECU assembly for 10 seconds or more.	Both conditions are met: The power switch is on (IG) for 10 seconds or more. The power source voltage of the power management control ECU is 10 V or more.	Turn the power switch on (IG) and wait at least 20 seconds.	-	DTC is stored until it is cleared using the Techstream.
U0155	Lost Communication with Combination Meter	The power management control ECU (power management CPU) does not receive data from the combination meter assembly for 3.1 seconds or more.	Both conditions are met: The power switch is on (IG) for 10 seconds or more. The power source voltage of the power management control ECU is 10 V or more.	Turn the power switch on (IG) and wait at least 20 seconds.	A message is displayed on the multi-information display for 15 seconds when the power switch is turned from on (IG) to off.	DTC is stored until it is cleared using the Techstream.
U0293*1	Lost Communication with HV ECU	The power management control ECU (power management CPU) does not receive data from the power management control ECU (HV CPU) for 3.1 seconds or more.	Both conditions are met: The power switch is on (IG) for 10 seconds or more. The power source voltage of the power management control ECU is 9.5 V or more.	Turn the power switch on (IG) and wait at least 13.1 seconds.	-	DTC is stored until it is cleared using the Techstream.

Power Management Control ECU / Techstream Display "Cruise Control"

Tech Tips