CAN COMMUNICATION SYSTEM(for LHD) HOW TO PROCEED WITH TROUBLESHOOTING

DTC Code	DTC Name
	HOW TO PROCEED WITH TROUBLESHOOTING

CAUTION / NOTICE / HINT

IMPORTANT POINTS CONCERNING 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.
- 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 the DTCs for the CAN communication system.
- 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 ignition switch off and leave the vehicle for 1 minute or more without operating the key, 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 ignition 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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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 CAN branch wire and V bus main bus circuits can be checked for malfunctions by inspecting at the DLC3 terminals using an electrical GTS.
  Note
  - When inspecting at the DLC3, do not connect the GTS 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 CAN main wire 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. 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.
6. 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.
7. 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 ignition switch can be turned 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 ignition switch off until the inspection of the vehicle is finished, as some fail-safe functions are canceled when the ignition switch is turned off.
If the ignition switch cannot be turned 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 ignition switch cannot be turned to ON even though the battery voltage is normal, repair this malfunction before performing troubleshooting.

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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 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. Example: ignition switch was turned off)

Points to be confirmed
Symptom	Air conditioning system Was the air conditioner operating Power steering system Was the power steering operating How was the electronic power steering force Did the steering feel strange at all Drive monitor display Did the display update properly Were numbers displayed for the estimated distance to empty Entry and start system Do the entry lock and unlock functions operate Does the entry warning system operate Do the lights turn on Was there any other system behavior that you noticed
Combination meter assembly warning lights	State of the warning lights and the order in which they illuminate Brake warning light / yellow (minor malfunction) or red (malfunction) ABS warning light SRS warning light EPS warning light SLIP warning light CRUISE indicator blinks Other lights Gauges/indicators in the combination meter Speedometer Tachometer Fuel gauge Shift indicator Other gauges or indicators

Result

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CHECK GTS OPERATION

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.

Check that the GTS and ECUs can communicate with the ignition switch ON.

Tech Tips

If communication is impossible, the GTS screen will indicate an error.
If communication between the GTS and ECUs is impossible, either the GTS or vehicle has a malfunction.
When communication between the GTS and the vehicle is impossible, but communication is possible when the GTS is connected to another vehicle, the vehicle has the malfunction. 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 battery voltage (11 V or more).
If communication between the GTS and ECUs is still impossible even when the GTS is connected to another vehicle, the GTS has a malfunction. Perform the self tests described in the GTS operator's 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 impossible 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 8 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 ignition switch ON, 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.

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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 FOR DLC3 CAN BRANCH WIRE AND V BUS MAIN WIRE (CANH - CANL)

Note

Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, 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.

Tech Tips

Operating the ignition 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 (-) battery terminal before measuring the resistances of the CAN main wire and the CAN branch wire.

*a	Front view of DLC3

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

Standard Resistance

Tester Connection	Condition	Specified Condition	Proceed to
G14-6 (CANH) - G14-14 (CANL)	Cable disconnected from negative (-) battery terminal	OK (54 to 69 Ω)	A
G14-6 (CANH) - G14-14 (CANL)	Cable disconnected from negative (-) battery terminal	NG (Higher than 70 Ω)	B
G14-6 (CANH) - G14-14 (CANL)	Cable disconnected from negative (-) battery terminal	NG (Below 53 Ω)	C

GO TO "Open in CAN Main Wire" Click here

GO TO "Short in CAN Bus Lines" Click here

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

*a	Front view of DLC3

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G14-6 (CANH) - G14-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
G14-14 (CANL) - G14-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Result

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OK
NG

GO TO "Short to B+ in CAN Bus Lines" Click here

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

*a	Front view of DLC3

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G14-6 (CANH) - G14-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
G14-14 (CANL) - G14-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

Result

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OK
NG

GO TO "Short to GND in CAN Bus Lines" 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 CAN communication are displayed (CAN bus circuit currently normal)	A
When sub bus 1 is selected from the bus selection screen, none of the connected ECUs (sensors) are detected DTC U1002 (network communication malfunction) is output by the main body ECU (multiplex network body ECU) (the sub bus 1 CAN main wire has an open or short circuit)	B
An ECU (sensor) that is supposed to be connected to the CAN communication system (V bus) is not detected and does not appear on the screen (the CAN branch wire of the ECU (sensor) has an open circuit or there is a loss of communication)	C
An ECU (sensor) that is supposed to be connected to the CAN communication system (sub bus 1) is not detected and does not appear on the screen (the CAN branch wire of the ECU (sensor) connected to sub bus 1 has an open circuit or there is a loss of communication) Note DTCs indicating a communication malfunction (DTCs that start with U) for the ECUs (sensors) connected to the CAN communication system (sub bus 1) are output by the main body ECU (multiplex network body ECU). Therefore, determine the location of the malfunction using those DTCs.	D
ECUs (sensors) that are supposed to be connected to the CAN communication system do not appear on the screen and other ECUs (sensors) appear and reappear on the screen during confirmation (one of the CAN branch wire of the ECU [sensor] has an open circuit)	E

Note

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 ECUs changes during the inspection, one of the CAN branch wires of a connected ECU or sensor may be open. (Signals from the ECU or sensor that has an open in one of its CAN branch wires create electrical noise, affecting response to the GTS and whether or not the ECUs and sensors are displayed.)
The main body ECU (multiplex network body ECU) checks for proper ECU communication for ECUs that are connected to the sub bus 1 and the results are displayed on the GTS. ECUs that stop communicating with the network gateway ECU for 3 seconds or more will stop being displayed on the GTS.

GO TO "DTC U1002" Click here

GO TO "Main Body ECU Communication Stop Mode" Click here

GO TO "PROBLEM SYMPTOMS TABLE" Click here

GO TO "Open in One Side of CAN Branch Line" Click here

CHECK RESULT OF CHECK 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).

CAN Bus Check

Check Result of Communication Malfunction Check (Select Malfunctioning Bus)

Inspection Result	Proceed to
While a DTC indicating a communication malfunction is not being output by a sub bus monitor ECU, the ECUs connected to the V bus have stored DTCs indicating a communication malfunction	A
DTC U1002 (network communication malfunction) is output by the main body ECU (multiplex network body ECU) (the sub bus 1 CAN main wire has an open or short circuit)	B
While DTC U1002 (network communication malfunction) is not being output by the main body ECU (multiplex network body ECU), DTCs indicating a malfunction in communication with ECUs (sensors) connected to sub bus 1 are output (a malfunction in the CAN branch wire for ECUs connected to sub bus 1 or a loss of communication)	C

Tech Tips

The term ''sub bus monitor ECU'' refers to a gateway function equipped ECU that is able to monitor a bus and store DTCs.

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When checking for communication DTCs, refer to How to Interpret Communication DTCs (DTCs that start with U).

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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.

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If communication DTCs are stored, and all ECUs and sensors connected to the CAN communication system are displayed on the Communication Bus Check (CAN bus check) screen of the GTS, a past malfunction that is currently not occurring is suspected.
Malfunctions in a CAN branch wire of the V bus are detected by the corresponding ECUs (sensors). Therefore, determine the location of the malfunction using the combination of output DTCs.
In order to check for malfunctions in sub bus 1, the main body ECU (multiplex network body ECU) checks for a loss of communication and other network communication problems with connected ECUs and stores DTCs when necessary.

GO TO "DTC U1002" 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.

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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.

Result

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Combination of DTCs is not in DTC Combination Table
Combination of DTCs is in DTC Combination Table

Combination of DTCs is in DTC Combination Table

GO TO COMMUNICATION STOP MODE TABLE Click here

Combination of DTCs is not in DTC Combination Table

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

Connect the cable to the negative (-) battery terminal.
Clear the DTCs using the GTS.
Perform a malfunction simulation test on all harnesses and connectors related to the V bus CAN main wire.

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 ignition switch off.

Result

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REPAIR AND REPLACE

Result

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CONFIRMATION TEST

Result

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CONFIRMATION TEST

Result

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END