CAN COMMUNICATION SYSTEM(w/o Toyota Safety Sense) 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 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 (-) auxiliary 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 (-) 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 communication 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 ECM, hybrid vehicle control ECU and brake booster with master cylinder assembly (skid control ECU).
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 ignition switch can be turned to 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 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 (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 ignition switch cannot be turned to 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 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	Electric power steering Normal A little heavier than usual There was no assist Air conditioning Whether the air conditioning system operated Whether the blower fan operated Wireless door lock function and smart entry function Whether the lock/unlock function operated Whether the illumination was turned on when the key was brought into a smart detection area Operation of other systems of concern
Meter warning lights	Illumination of warning lights and the order in which they illuminated Master Check engine (MIL) ABS SLIP Brake EPS SRS Others Meter display Speedometer Hybrid system indicator

Result

Result
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CHECK GTS OPERATION

Tech Tips

Read the GTS operators manual before use.

Click here

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

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

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 auxiliary 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 the malfunction. Perform the self tests described in the GTS operators manual. (The GTS may be malfunctioning or its auxiliary 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 7 Click here

Refer to GTS operator's manual

CHECK DTC

Using the GTS, perform All Codes 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, the sensor itself also cause these DTCs to be output.
- If a CAN communication line connector is disconnected with the ignition 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

Result
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CHECK COMMUNICATION MALFUNCTION DTCs (CONNECTION STATUS CHECK USING GTS)

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

Record all the DTCs stored for ECUs and sensors.

Result

Result
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CHECK COMMUNICATION BUS CHECK (CONNECTION STATUS CHECK USING GTS)

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

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

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

Result

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 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 (-) auxiliary 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.

*1 DLC3

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

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

Standard Resistance

Tester Connection	Condition	Specified Condition
F3-6 (CANH) - F3-14 (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 (LHD Models) Click here

GO TO OPEN IN CAN MAIN BUS LINE (RHD Models) Click here

GO TO SHORT IN CAN BUS LINES (LHD Models) Click here

GO TO SHORT IN CAN BUS LINES (RHD Models) 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
F3-6 (CANH) - F3-4 (CG)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher
F3-14 (CANL) - F3-4 (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 (LHD Models) Click here

GO TO SHORT TO GND IN CAN BUS LINE (RHD Models) 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
F3-6 (CANH) - F3-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher
F3-14 (CANL) - F3-16 (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 (LHD Models) Click here

GO TO SHORT TO +B IN CAN BUS LINE (RHD Models) Click here

CHECK RESULT OF COMMUNICATION 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 Communication Bus Check was performed).

Result

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
When the V bus is selected using the drop down list, 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.)	B
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.)	C
One of the ECUs and sensors connected to the V Bus is not displayed on the screen. (Open in ECU or sensor branch lines, or communication is interrupted.)	D
One of the ECUs and sensors connected to sub bus 15 is not displayed on the screen. (Open in ECU or sensor branch lines, or communication is interrupted.)	E
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.)	F

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 Communication Bus Check, refer to How to Interpret CAN Bus Diagnosis (Communication Bus Check) Screen.

Click here
If the detection status of ECUs 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 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.

GO TO U0100, U0129, U0293 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 CHECK COMMUNICATION MALFUNCTION DTCs (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).

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.)

The ECM has not output DTC U0293 (Lost Communication with HV ECU).
The hybrid vehicle control ECU has not output DTC U0100 (Lost Communication with ECM/PCM "A") or DTC U0129 (Lost Communication with Brake System Control Module (U0129)).
The brake booster with master cylinder assembly (skid control ECU) has not output DTC U0293 (Lost Communication with HV ECU).

ECUs connected to sub bus 15 store communication error DTCs.

(A malfunction occurred in sub bus 15.)

The ECM outputs only DTC U0293 (Lost Communication with HV ECU).
The hybrid vehicle control ECU outputs only DTC U0100 (Lost Communication with ECM/PCM "A") and DTC U0129 (Lost Communication with Brake System Control Module).
The brake booster with master cylinder assembly (skid control ECU) outputs only DTC U0293 (Lost Communication with HV ECU).

The hybrid vehicle control ECU outputs only DTC U0129 (Lost Communication with Brake System Control Module).

(A malfunction occurred in an ECU branch line connected to sub bus 15.)

Tech Tips

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

Click here
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.
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.

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 "Communication Bus Check" 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 ignition switch off.

Result

Proceed to
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REPAIR OR REPLACEMENT

Result

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NEXT

CONFIRMATION TEST

Result

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END