CAN COMMUNICATION SYSTEM HOW TO PROCEED WITH TROUBLESHOOTING

DTC Code	DTC Name
	HOW TO PROCEED WITH TROUBLESHOOTING

CAUTION / NOTICE / HINT

PRECAUTIONS WHEN TROUBLESHOOTING
Note
- 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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- Refer to Diagnosis System for CAN communication system DTCs.
- Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output.
- Before measuring the resistance of the CAN bus, turn the power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
- After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.
  
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1. CAN communication DTCs are output for CAN main bus and CAN branch malfunctions as well as for internal malfunctions or power source malfunctions of ECUs or sensors for systems using CAN communication. Therefore, when DTCs for internal malfunctions or power source malfunctions of corresponding systems are output at the same time as CAN communication DTCs, troubleshoot according to the internal malfunction and power source malfunction DTCs.
2. The DLC3 branch and V bus main bus circuits can be checked for malfunctions by inspecting at the DLC3 terminals using an electrical tester.
  Note
  - When inspecting at the DLC3 connector, do not connect the tester directly to the terminals. Instead, connect using service wires.
  - Inspections for an open in an ECU or sensor branch, or inspections for buses other than the V bus cannot be performed from the DLC3.
3. An open in a branch for ECUs or sensors that are connected to the CAN main bus can be checked by performing a CAN bus check using the GTS. (This inspection is possible when the DLC3 branch and V bus main bus lines are normal.)
4. If the V bus had a communication error, the probable ECU or sensor for which communication stopped can be determined using the combination of communication DTCs (DTCs that start with U) that are output.
5. A malfunction of sub bus 15 can be determined based on the number of DTCs stored by the hybrid vehicle control ECU assembly, ECM and skid control ECU assembly.
6. If a sub bus has a communication error, the gateway function equipped ECU (sub bus monitor ECU) detects it and stores DTCs related to the error.
  
  Tech Tips
  
  On the GTS, gateway function equipped ECUs display DTCs for ECUs connected to the sub bus.
7. When an open circuit is detected, before disconnecting related connectors for inspection, push in on the connector body to check that the connector is not loose or disconnected.
8. When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.

PROCEDURE

VEHICLE BROUGHT TO WORKSHOP

Tech Tips

If the power switch can be turned on (IG) (the power source mode can be changed to on (IG)) 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 power switch off until the inspection of the vehicle is finished, as some fail-safe functions are canceled when the power switch is turned off.
If the power switch cannot be turned on (IG) (the power source mode cannot be changed to on (IG)) when the vehicle is brought in, measure the voltage of the auxiliary battery. If the voltage is below 11 V, recharge or replace the auxiliary battery before performing troubleshooting.
If the power switch cannot be turned on (IG) even though the auxiliary battery voltage is normal, repair this malfunction before performing troubleshooting.

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Result

Result
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CUSTOMER PROBLEM ANALYSIS

Tech Tips

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.)

It is useful to confirm the symptoms and the conditions in which the vehicle was operating at the time when a malfunction occurred. This helps to narrow down the malfunctioning part.

Tech Tips

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.)
Return conditions (what made the vehicle return to normal, for example, the power switch was turned off)

Points to be confirmed
Symptom	Electric power steering - Normal - A little heavier than usual - There was no assist Air conditioning - Whether the air conditioning system operated - Whether the air conditioning function can be operated by the LEXUS display audio controller or Remote Touch - Whether the blower fan operated Drive monitor display - Whether the update of multi-information display items stopped - Whether the numeric part of the drivable distance was not displayed Eco navigation (eco drive) display - Whether the average fuel consumption graph is updated every minute - Whether the updated section average fuel consumption graph is displayed - Whether the distance-to-empty is displayed on the section average fuel consumption graph display Footwell lights - Whether the footwell illumination changed when a door was opened/closed - Whether the footwell lights turned off when the power switch is turned on (IG) Auto lock and unlock operation - Whether the speed linked auto-lock function operated while driving - Whether the unlock function operated when the shift lever was moved to P Wireless door lock function and smart entry function - Whether the lock/unlock function operated - Whether the entry warning function operated - Whether the illumination was turned on when the key was brought into a smart detection area Power tilt and telescopic system - Whether the driving position memory/restoring, auto away/return functions operated Seat - Whether the driving position memory call, auto away/return functions operated Operation of other systems of concern
Meter warning lights	Illumination of warning lights and the order in which they illuminated - Check engine (MIL) - ABS - SRS - EPS - Slip - Master - Brake - Auto leveling - PCS - Cruise - Others Meter display - Speedometer - Tachometer - Hybrid system indicator Content displayed on the multi-information display - Whether a warning message is displayed on the multi-information display

Result

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CHECK GTS OPERATION

Tech Tips

Read the GTS operators manual before use.

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Connect the GTS to the DLC3.
Turn the power switch on (IG).
Turn the GTS on.

Check that the GTS and ECUs can communicate with the power switch on (IG).

Tech Tips

If communication is not possible, the GTS screen will indicate an error.
If communication between the GTS and ECUs is not possible, either the GTS or vehicle has a malfunction.
When communication between the GTS and the vehicle is not possible, but communication is possible when the GTS is connected to another vehicle, the vehicle is malfunctioning. Inspect the CANH and CANL branch lines of the DLC3 and the ECU power source circuits (in this case perform steps 7 to 9 first). In addition, check that the BAT terminal of the DLC3 receives auxiliary battery voltage (11 V or more).
If communication between the GTS and ECUs is still not possible even when the GTS is connected to another vehicle, the GTS has a malfunction. Perform the self tests described in the GTS operators manual. (The GTS may be malfunctioning or its battery may be discharged.)

Result

Result	Proceed to
OK (Communication between the GTS and the vehicle is possible.)	A
OK (Communication between the GTS and the vehicle is not possible but communication is possible when connected to another vehicle.)	B
NG (Communication is not possible between the GTS and the vehicle, nor between the GTS and another vehicle.)	C

GO TO STEP 7 Click here

REFER TO GTS OPERATOR'S MANUAL

CHECK DTC

Using the GTS, perform Health Check to read current and history DTCs and record them.
Note
- 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 power switch on (IG), the ECUs of the corresponding system and related systems store a DTC.
Tech Tips
- If an open in a CAN main bus line, a short between the CAN bus lines (CANH and CANL) or a +B or ground short in a CAN bus occurs, DTCs of almost all ECUs and sensors on the CAN bus may be output (or a message indicating a communication error may be displayed on the GTS screen). In this case, check the resistance of the CAN bus (steps 7 to 9) first.
- If an open occurs in just one of the lines of a CAN branch, DTCs which are not related to malfunctioning parts may be output (DTCs may be displayed randomly), or a message indicating a communication error may be displayed on the GTS.

Read the freeze frame data using the GTS and record it.

Result

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PERFORM COMMUNICATION MALFUNCTION CHECK (CONNECTION STATUS CHECK USING GTS)

Select "Communication Malfunction Check" from the screen on the GTS.

Record all the DTCs stored for ECUs and sensors.

Result

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PERFORM CAN BUS CHECK (CONNECTION STATUS CHECK USING GTS)

Based on the vehicle equipment and specifications, confirm the systems that use CAN communication.

Click here
Select "CAN Bus Check" from the screen on the GTS.

CAN Bus Check

Observe the screen for approximately 2 minutes to check the ECUs and sensors displayed on the screen.

Result

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CHECK DLC3 BRANCH LINE AND V BUS MAIN LINE (CANH - CANL)

Note

Before measuring the resistance of the CAN bus, turn the power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.

Tech Tips

Operating the power switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.

Disconnect the cable from the negative (-) auxiliary battery terminal.

DLC3

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
K9-6 (CANH) - K9-14 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

Result

Result	Proceed to
OK	A
NG (70 Ω or higher) (LHD Models)	B
NG (70 Ω or higher) (RHD Models)	C
NG (Below 54 Ω) (LHD Models)	D
NG (Below 54 Ω) (RHD Models)	E

GO TO OPEN IN CAN MAIN BUS LINE Click here

GO TO SHORT IN CAN BUS LINES Click here

CHECK FOR SHORT TO GND IN V BUS (CANH, CANL - CG)

DLC3

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
K9-6 (CANH) - K9-4 (CG)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher
K9-14 (CANL) - K9-4 (CG)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher

Result

Result	Proceed to
OK	A
NG (LHD Models)	B
NG (RHD Models)	C

GO TO SHORT TO GND IN CAN BUS LINE Click here

CHECK FOR SHORT TO +B IN V BUS (CANH, CANL - BAT)

DLC3

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
K9-6 (CANH) - K9-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher
K9-14 (CANL) - K9-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher

Result

Result	Proceed to
OK	A
NG (LHD Models)	B
NG (RHD Models)	C

GO TO SHORT TO +B IN CAN BUS LINE Click here

CHECK RESULT OF CAN BUS CHECK (CONNECTION STATUS CHECK USING GTS)

Inspect or repair the probable malfunctioning part based on the check result of step 6 (the step in which CAN bus check was performed).

CAN Bus Check

Result of CAN Bus Check (Connection Status Check Using GTS)

Result	Proceed to
All ECUs and sensors connected to the CAN communication system are displayed on the screen. (CAN bus circuit is currently normal.)	A
All ECUs except the main body ECU (multiplex network body ECU) connected to sub bus 1 are not displayed on the screen. The main body ECU (multiplex network body ECU) (Main Body) outputs DTC U1002. (Open or short in sub bus 1 main lines.)	B
All ECUs except the network gateway ECU connected to sub bus 2 are not displayed on the screen. The network gateway ECU (Gateway) outputs DTC U1002. (Open or short in sub bus 2 main lines.)	C
All ECUs except the driving support ECU assembly connected to sub bus 13 are not displayed on the screen. The driving support ECU assembly (Pre-crash 2) outputs DTC U1002. (Open or short in sub bus 13 main lines.)	D
When the V bus is selected using the pull down menu, all the ECUs and sensors connected to the V bus are displayed on the screen, but when sub bus 15 is selected, no connected ECUs or sensors are displayed. (Open or short in sub bus 15 main lines.)	E
All ECUs connected to sub bus 1 are not displayed on the screen. (Open in main body ECU (multiplex network body ECU) branch lines or main body ECU (multiplex network body ECU) malfunction.)	F
All ECUs connected to sub bus 2 are not displayed on the screen. (Open in network gateway ECU branch lines or network gateway ECU malfunction.)	G
No ECUs or sensors connected to the ECM or sub bus 15 are displayed on the screen. (Open in ECM main lines or ECM malfunction.)	H
One of the ECUs or sensors connected to the V Bus is not displayed on the screen. (Open in ECU or sensor branch lines, or communication is interrupted.)	I
One of the ECUs or sensors connected to sub bus 1 is not displayed on the screen.* (Open in ECU or sensor branch lines, or communication interrupted.) One of the ECUs or sensors connected to sub bus 2 is not displayed on the screen.* (Open in ECU or sensor branch lines, or communication interrupted.) One of the ECUs or sensors connected to sub bus 15 is not displayed on the screen. (Open in ECU or sensor branch lines, or communication interrupted.)	J
In addition to ECUs and sensors which are connected to the CAN communication system but are not displayed on the screen, there are ECUs or sensors for which the detection status changes (changes between detected and not detected) during the inspection. (Open in one side of ECU or sensor branch lines.)	K

Note

*: In this case, as the main body ECU (multiplex network body ECU) (Main Body), network gateway ECU (Gateway) or driving support ECU assembly (Pre-Crash 2) outputs communication DTCs (DTCs that start with U), the problem area can be determined from those DTCs.
Non-installed ECUs or sensors will not be displayed. Do not mistake them for being in communication stop mode.
It may be possible to select buses that do not have ECUs or sensors from the bus selection pull-down menu on the GTS. 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.)

Tech Tips

Regarding CAN Bus Check, refer to How to Interpret CAN Bus Check Screen.

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If the detection status of any ECU changes during the inspection, one of the branch lines of a connected ECU or sensor may be open. (Signals from the ECU or sensor that has an open in one of its branch lines create electrical noise, affecting response to the GTS and whether or not the ECUs and sensors are displayed.)
Regarding the ECUs connected to sub bus 1, the main body ECU (multiplex network body ECU) displays communicating ECUs on the GTS. If the communication between the main body ECU (multiplex network body ECU) and an ECU stops for 10 seconds or more, the ECU will no longer be displayed on the GTS.
Regarding the ECUs connected to sub bus 2, the network gateway ECU displays communicating ECUs on the GTS. If the communication between the network gateway ECU and an ECU stops for 10 seconds or more, the ECU will no longer be displayed on the GTS.
Regarding the ECUs connected to sub bus 13, the driving support ECU assembly displays communicating ECUs on the GTS. If the communication between the driving support ECU assembly and an ECU stops for 10 seconds or more, the ECU will no longer be displayed on the GTS.
Regarding the communication stop mode for ECUs connected to sub bus 1, refer to the inspection procedure for the DTCs that indicate a communication stop.
Regarding the ECUs connected to sub bus 15, the ECM displays communicating ECUs on the GTS. If the communication between the ECM and an ECU stops for 3 seconds or more, the ECU will no longer be displayed on the GTS.
Regarding the communication stop mode for ECUs connected to sub bus 2, refer to the inspection procedure for the DTCs that indicate a communication stop.
Regarding the communication stop mode for ECUs connected to sub bus 13, refer to the inspection procedure for the DTCs that indicate a communication stop.

GO TO U1002 (Main Body) Click here

GO TO U1002 (Gateway) Click here

GO TO U1002 (Pre-crash 2) Click here

GO TO U0100, U0129, U0293 Click here

GO TO MAIN BODY ECU COMMUNICATION STOP MODE Click here

GO TO GATEWAY ECU COMMUNICATION STOP MODE Click here

GO TO ECM COMMUNICATION STOP MODE Click here

GO TO COMMUNICATION STOP MODE TABLE Click here

GO TO DIAGNOSTIC TROUBLE CODE CHART Click here

GO TO OPEN IN ONE SIDE OF CAN BRANCH LINE Click here

CHECK RESULT OF COMMUNICATION MALFUNCTION CHECK (SELECT THE MALFUNCTIONING BUS)

Inspect or repair the probable malfunctioning part based on the check result of step 5 (the step in which checking for communication malfunction DTCs was performed).

Check Result of Communication Malfunction Check (Select Malfunctioning Bus)

Result	Proceed to
The sub bus monitor ECU has not output communication DTCs but ECUs connected to the V bus have stored communication DTCs. (A malfunction occurred in the V Bus.) ECUs connected to sub bus 15 have not output communication DTCs but ECUs connected to the V bus have stored communication DTCs. (A malfunction occurred in the V Bus.) The ECM (Engine and ECT) has not output DTC U0293 (Lost Communication with Hybrid Vehicle Control System). The hybrid vehicle control ECU assembly (Hybrid Control) has not output DTC U0100 (Lost Communication with ECM/PCM "A") or DTC U0129 (Lost Communication with Brake System Control Module). The skid control ECU assembly (ABS/VSC/TRC) has not output DTC U0293 (Lost Communication with Hybrid Vehicle Control System).	A
The main body ECU (multiplex network body ECU) outputs DTC U1002. (A malfunction occurred in sub bus 1.)	B
The network gateway ECU (Gateway) outputs DTC U1002. (A malfunction occurred in sub bus 2.)	C
The driving support ECU assembly (Pre-crash 2) outputs DTC U1002. (A malfunction occurred in sub bus 13.)	D
ECUs connected to sub bus 15 output communication error DTCs. (A malfunction occurred in sub bus 15.) The ECM (Engine and ECT) outputs only DTC U0293 (Lost Communication with Hybrid Vehicle Control System). The hybrid vehicle control ECU assembly (Hybrid Control) outputs only DTC U0100 (Lost Communication with ECM/PCM "A") and DTC U0129 (Lost Communication with Brake System Control Module). The skid control ECU assembly (ABS/VSC/TRC) outputs only DTC U0293 (Lost Communication with Hybrid Vehicle Control System).	E
The main body ECU (multiplex network body ECU) outputs DTCs other than DTC U1002. (A malfunction occurred in an ECU branch line connected to sub bus 1.) The network gateway ECU outputs DTCs other than DTC U1002. (A malfunction occurred in an ECU branch line connected to sub bus 2.) The driving support ECU assembly outputs DTCs other than DTC U1002. (A malfunction occurred in an ECU branch line connected to sub bus 13.) The hybrid vehicle control ECU assembly (Hybrid Control) outputs only DTC U0129 (Lost Communication with Brake System Control Module). (A malfunction occurred in an ECU branch line connected to sub bus 15.)	F

Tech Tips

Only sub bus 1, sub bus 2 and sub bus 13 have a sub bus monitor ECU.
The term ''sub bus monitor ECU'' refers to a gateway function equipped ECU that is able to monitor a bus and store DTCs.
When checking for communication DTCs, refer to How to Interpret Communication DTCs (DTCs that start with U).

Click here
Because a gateway function equipped ECU (sub bus monitor ECU) monitors signals from all ECUs that are connected to its sub bus, a gateway function equipped ECU can detect ECUs with a communication stop more accurately. In this case, perform troubleshooting by referring to the DTC combination table for the sub bus.

Click here
If communication DTCs are stored, and all ECUs and sensors connected to the CAN communication system are displayed on the CAN Bus Check screen of the GTS, a past malfunction that is currently not occurring is suspected.
When a CAN branch of the V bus is malfunctioning, because the ECUs and sensors related to it detect the malfunction, the problem area can be determined using the combination of DTCs that are output.
When sub bus 1 is malfunctioning, the main body ECU (multiplex network body ECU) detects a communication stop for connected ECUs and a network communication error, and stores DTCs.
When sub bus 2 is malfunctioning, the network gateway ECU detects a communication stop for connected ECUs and a network communication error, and stores DTCs.
When sub bus 13 is malfunctioning, the driving support ECU assembly detects a communication stop for connected ECUs and a network communication error, and stores DTCs.
On the GTS, the Main Body item displays the DTCs for ECUs connected to sub bus 1.
On the GTS, the Gateway item displays the DTCs for ECUs connected to sub bus 2.
On the GTS, the Pre-Crash 2 item displays the DTCs for ECUs connected to sub bus 13.
When both the sub bus monitor ECU and the ECUs connected to the V bus store communication DTCs, check and repair the corresponding sub bus first.

GO TO U1002 (Main Body) Click here

GO TO U1002 (Gateway) Click here

GO TO U1002 (Pre-crash 2) Click here

GO TO U0100, U0129, U0293 Click here

GO TO DIAGNOSTIC TROUBLE CODE CHART Click here

DTC COMBINATION TABLE

Confirm the problem according to the combination of output DTCs regarding the CAN communication system.

Click here

Result

Result	Proceed to
Combination of DTCs is not in DTC Combination Table	A
Combination of DTCs is in DTC Combination Table	B

Tech Tips

CAN communication system history DTCs may indicate the problem if CAN communication system DTCs are output and all ECUs and sensors connected to the CAN communication system are displayed on the CAN Bus Check screen of the GTS.

GO TO COMMUNICATION STOP MODE TABLE Click here

IDENTIFICATION OF PROBLEM (PAST MALFUNCTION IN MAIN BUS OF V BUS)

Connect the cable to the negative (-) auxiliary battery terminal.
Clear the DTCs using the GTS.
Perform the tests in Symptom Simulation to check the wire harnesses and connectors including those for V bus main bus lines.

Click here

Based on the results of the check, inspect the parts that output DTCs to determine the malfunctioning part.

Tech Tips

If DTCs are output, do not turn the power switch off.

Result

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REPAIR OR REPLACEMENT

Result

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CONFIRMATION TEST

Result

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END