How To Proceed With Troubleshooting

Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the main wire and the branch wire.

HINT:

• Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
• * Use the intelligent tester or Techstream

1. VEHICLE BROUGHT TO WORKSHOP 
2. INSPECT BATTERY VOLTAGE 

   Standard voltage: 11 to 14 V 

   If the voltage is below 11V, recharge or replace the battery before proceeding

3. CHECK AND CLEAR DTC* 
   1. Using the intelligent tester or Techstream, perform the ALL DTC check.
   NOTE:

   • If a CAN communication malfunction code that informs that an ECU or sensor has a power malfunction or interior malfunction is causing a communication stop, the problem may not be in the communication line. There is a high possibility that the ECU or sensor has a signal transmission failure. Therefore, first troubleshoot any DTCs related to the ECU or sensor.
   • When CAN communication related connectors are disconnected with the power switch ON (IG or ACC), the ECU related to the connector and ECUs of related systems will store a CAN communication DTC.
4. CHECK INSTALLED SYSTEMS (ECU AND SENSOR) THAT USE CAN COMMUNICATION 
   1. Based on the vehicle equipment and specifications, confirm the systems that use CAN communication (see DIAGNOSIS SYSTEM ).
5. CHECK ECUS CONNECTED TO CAN BUS (USING INTELLIGENT TESTER OR TECHSTREAM)* 
   1. for Intelligent Tester
      1. Select "CAN BUS CHECK" from the "OBD/MOBD MENU" (see DIAGNOSIS SYSTEM ).
      2. Press "ENTER" on the intelligent tester (see DIAGNOSIS SYSTEM ).
   2. for Techstream
      1. Select "CAN Bus Check" from the "System Select".
   3. Wait 1 minute and then check the display of the connected ECUs and sensors.
   INSPECTION RESULT REFERENCE
   
   

   Inspection Result	Proceed to
   No ECUs or sensors are displayed (V bus main wire open or short malfunction, or DLC3 branch wire malfunction)	A
   Except for main body ECU, no ECUs connected to MS bus are displayed Main body ECU outputs MS bus malfunction code (U1002) (MS bus main wire open or short malfunction)	B
   No ECUs connected to MS bus are displayed (branch wire between main body ECU and V bus circuit is open)	C
   Except for ECM, no ECUs connected to braking and driving bus are displayed ECM outputs braking and driving bus malfunction code (U1004) (braking and driving bus main wire open or short malfunction)	D
   No ECUs connected to braking and driving bus are displayed (branch wire between ECM and V bus is open)	E
   Except for skid control ECU, no ECUs connected to steering bus are displayed Skid control ECU outputs steering bus malfunction code (U1005) (steering bus circuit main wire open or short malfunction)	F
   No ECUs connected to steering bus are displayed (branch wire between skid control ECU and V bus is open)	G
   ECU or sensor that should be connected to CAN communication is not displayed (ECU or sensor branch wire open)	H
   ECU or sensor that should be connected to CAN communication is not displayed or display is intermittent during check (ECU or sensor branch wire open on one side)	I
   All ECUs and sensors connected to CAN communication system displayed on screen	J

   NOTE: ECUs and sensors that are not present will not be displayed. Be careful not to mistake them for communication stop malfunctions.

   HINT:

   • If the display of an ECU is intermittent during the check, one side of an ECU or sensor branch wire is open (The signal of the ECU is treated as noise, which affects the response and display of the intelligent tester or Techstream).
   • The main body ECU checks for proper ECU communication for ECUs that are connected to the CAN MS bus circuit, and the results are displayed on the intelligent tester or Techstream.
   • The gateway ECU built into the main body ECU may be malfunctioning if both of the following occurs. 1) all ECUs connected to the MS bus are not displayed on the tester, and 2) DTC U1002 is not output.
   • The ECM checks for proper ECU communication for ECUs that are connected to the braking and driving bus, and the results are displayed on the intelligent tester or Techstream.
   • The gateway ECU built into the ECM may be malfunctioning if both of the following occurs 1) all ECUs connected to the braking and driving bus are not displayed on the tester, and 2) DTC U1004 is not output.
   • The skid control ECU checks for proper ECU communication for ECUs that are connected to the steering bus, and the results are displayed on the intelligent tester or Techstream.
   • The gateway ECU built into the skid control ECU may be malfunctioning if both of the following occurs 1) all ECUs connected to the steering bus are not displayed on the tester, and 2) DTC U1005 is not output.
   • If communication stops between an ECU and the main body ECU, ECM, skid control ECU or driving support ECU for 10 seconds or more, the ECU disappears from the intelligent tester or Techstream display.
   • For communication stop mode of ECUs connected to the CAN MS bus circuit, steering bus, or braking and driving bus, refer to the DTC flowchart of the respective communication stop.

   B:  GO TO DTC U1002 FLOWCHART

   C:  GO TO MAIN BODY ECU COMMUNICATION STOP MODE FLOWCHART

   D:  GO TO DTC U1004 FLOWCHART

   E:  GO TO ECM COMMUNICATION STOP MODE FLOWCHART

   F:  GO TO DTC U1005 FLOWCHART

   G:  GO TO SKID CONTROL ECU COMMUNICATION STOP MODE FLOWCHART

   H:  GO TO PROBLEM SYMPTOMS TABLE 

   I:  GO TO OPEN IN ONE SIDE OF CAN BRANCH WIRE FLOWCHART

   J:  GO TO STEP  10

   A: Go to Next Step 

6. CHECK DLC3 BRANCH WIRE AND V BUS CIRCUIT MAIN WIRE (CANH - CANL) 
   1. Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the main wire and the branch wire.
      NOTE: When disconnecting the cable, some systems need to be initialized after the cable is reconnected (see INITIALIZATION ).
   2. Measure the resistance of the DLC3.

   Standard resistance 

   RESISTANCE SPECIFICATION
   
   

   Tester Connection	Switch Condition	Specified Condition	Proceed to
   6 (CANH) - 14 (CANL)	Power switch OFF	OK (54 to 69 Ω)	A
   6 (CANH) - 14 (CANL)	Power switch OFF	NG (70 Ω or higher)	B
   6 (CANH) - 14 (CANL)	Power switch OFF	NG (less than 54 Ω)	C

   Fig 1: Identifying DLC3 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   B:  GO TO CAN MAIN WIRE FOR DISCONNECTION

   C: GO TO CHECK CAN BUS LINES FOR SHORT CIRCUIT 

   A: Go to Next Step 

7. CHECK V BUS CIRCUIT +B (CANH, CANL - BAT) 
   1. Measure the resistance of the DLC3.

   Standard resistance 

   RESISTANCE SPECIFICATION
   
   

   Tester Connection	Switch Condition	Specified Condition
   6 (CANH) - 16 (BAT)	Power switch OFF	6 kΩ or higher
   14 (CANL) - 16 (BAT)	Power switch OFF	6 kΩ or higher

   NG: GO TO CHECK CAN BUS LINE FOR SHORT TO +B 

   Fig 2: Identifying DLC3 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK: Go to Next Step 

8. CHECK V BUS CIRCUIT GND (CANH, CANL - CG) 
   1. Measure the resistance of the DLC3.

   Standard resistance 

   RESISTANCE SPECIFICATION
   
   

   Tester Connection	Switch Condition	Specified Condition
   6 (CANH) - 4 (CG)	Power switch OFF	200 Ω or higher
   14 (CANL) - 4 (CG)	Power switch OFF	200 Ω or higher

   NG: GO TO CHECK CAN BUS LINE FOR SHORT TO GND 

   Fig 3: Identifying DLC3 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK: Go to Next Step 

9. CHECK COMMUNICATION MALFUNCTION DTC (PAST DTC CHECK)* 
   1. for Intelligent Tester
      1. Select "CAN BUS CHECK" from the "OBD/MOBD MENU" (see DIAGNOSIS SYSTEM ).
      2. Press "ENTER" on the intelligent tester (see DIAGNOSIS SYSTEM ).
   2. for Techstream
      1. Select "CAN Bus Check" from the "System Select"
   3. Write down all of the DTCs stored in each ECU.

      HINT:

      • If there are communication malfunction DTCs stored but the intelligent tester's or Techstream's "CAN Bus Check - Communication Bus Check" screen displays all of the ECUs and sensors connected to the CAN system, the communication malfunction DTCs may be past malfunctions that are no longer present.
      • For V bus main wire malfunctions, related ECUs are also detected Therefore, determine the malfunctioning area based on all of the DTCs that are output.
      • For MS bus malfunctions, DTCs are output based on the detection of communication stop malfunctions and network malfunctions of ECUs that are connected by the main body ECU.
      • For braking and driving bus malfunctions, DTCs are output based on the detection of communication stop malfunctions and network malfunctions of ECUs that are connected by the ECM.
      • For steering bus malfunctions, DTCs are output based on the detection of communication stop malfunctions and network malfunctions of ECUs that are connected by the skid control ECU.
   INSPECTION RESULT REFERENCE
   
   

   Inspection Result	Proceed to
   ECU connected to V bus main wire has stored communication malfunction code (V bus main wire past malfunction)	A
   Main body ECU outputs MS bus malfunction code (U1002) (MS bus past malfunction)	B
   Main body ECU outputs malfunction code other than MS bus malfunction code (U1002) (past malfunction of ECU branch wire connected to MS bus)	C
   ECM outputs network malfunction code (U1004) (braking and driving bus past malfunction)	D
   ECM outputs malfunction code other than network malfunction code (U1004) (past malfunction of branch wire connected to braking and driving bus)	E
   Skid control ECU outputs network malfunction code (U1005) (steering bus past malfunction)	F
   Skid control ECU outputs malfunction code other than network malfunction code (U1005) (past malfunction of ECU branch wire connected to steering bus)	G

   B:  GO TO DTC U1002 FLOWCHART

   C:  GO TO PROBLEM SYMPTOMS TABLE 

   D:  GO TO DTC U1004 FLOWCHART

   E:  GO TO PROBLEM SYMPTOMS TABLE 

   F:  GO TO DTC U1005 FLOWCHART

   G:  GO TO PROBLEM SYMPTOMS TABLE 

   A: Go to Next Step 

10. CHECK DTC COMBINATION TABLE (V BUS CIRCUIT BRANCH WIRE OPEN PAST MALFUNCTION) 
    1. Based on the combination of stored CAN communication system DTCs, determine which ECUs and sensors have a communication stop malfunction (see DIAGNOSIS SYSTEM )
11. PERFORM MALFUNCTION SIMULATION TEST (V BUS CIRCUIT MAIN WIRE PAST MALFUNCTION)* 
    1. Using the intelligent tester or Techstream, clear all DTCs.
    2. Perform a malfunction simulation test on all harnesses and connectors related to the V bus circuit main wire.
    3. Check the DTCs that were output as a result of the malfunction simulation test. Then determine the malfunctioning area.
12. ADJUST, REPAIR AND REPLACE 
13. CONFIRMATION TEST 

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