CAN COMMUNICATION SYSTEM(w/o Toyota Safety Sense) Check CAN Bus Lines for Short Circuit (LHD Models)

DESCRIPTION

There may be a short circuit between the V bus main lines and/or CAN branch lines when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 54 Ω.

Symptom Trouble Area
Resistance between terminals 6 (CANH) and 14 (CANL) of DLC3 is below 54 Ω.

  • Short in CAN main bus line

  • Short in CAN branch line

  • ECM

  • Brake booster with master cylinder assembly (Skid control ECU)

  • Main body ECU (Multiplex network body ECU)

  • Air conditioning amplifier assembly

  • Power steering ECU assembly

  • Smart key ECU assembly (Certification ECU)*1

  • Airbag sensor assembly

  • Spiral cable with sensor sub-assembly (Steering sensor)

  • Hybrid vehicle control ECU

  • Combination meter assembly

  • Radio and display receiver assembly*2

  • CAN junction connector LH

  • CAN junction connector RH

WIRING DIAGRAM

A004EAGE01
A004FVOE01

CAUTION / NOTICE / HINT

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.

  • 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 Click here.

  • 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 Click here.

  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

  • DTC check procedure: Turn the ignition switch to ON (IG), turn the cruise control system on using the cruise control main switch (ON/OFF switch), wait at least 60 seconds, and then drive the vehicle at a speed of 20 km/h (12 mph) or more.

  • After the repair, perform Communication Bus Check and check that all the ECUs and sensors connected to the CAN communication system are displayed Click here.

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.

  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

  • Connectors that connect to the CAN junction connector can be distinguished by color of their CAN bus lines. When the connectors have been disconnected from the CAN junction connector, reconnecting the connectors to non-original positions on the CAN junction connector does not affect system performance. However, it is preferred to reconnect the connectors to their original positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

PROCEDURE


  1. CHECK FOR SHORT IN CAN BUS LINES (COMBINATION METER ASSEMBLY - CAN J/C RH)


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

    2. A004EWEE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Combination Meter Assembly)

      Disconnect the combination meter assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      F1-32 (CANH) - F1-31 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω

      Tech Tips

      If the resistance becomes normal (between 108 to 132 Ω) when the connector is disconnected, there may be a short in the combination meter assembly.


    OK

    REPLACE COMBINATION METER ASSEMBLY Click here

    NG

  2. CHECK FOR SHORT IN CAN BUS LINES (ECM - CAN J/C LH)


    1. Reconnect the F1 combination meter assembly connector.

    2. Disconnect the ECM connector.

    3. A004E66E02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to ECM)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A28-13 (CANH) - A28-26 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω

      Tech Tips

      If the resistance becomes normal (between 108 to 132 Ω) when the connector is disconnected, there may be a short in the ECM.


    OK

    REPLACE ECM Click here

    NG

  3. CHECK FOR SHORT IN CAN BUS LINES (CAN J/C RH)


    1. Reconnect the A28 ECM connector.

    2. Disconnect the CAN junction connector RH.

    3. A004EUEE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to CAN Junction Connector RH)
      *b to Spiral Cable with Sensor Sub-assembly (Steering Sensor)
      *c to Smart Key ECU Assembly (Certification ECU) (w/ Power Switch)
      *d to Airbag Sensor Assembly
      *e to Radio and Display Receiver Assembly (w/ Display)
      *f to Combination Meter Assembly
      *g to Air Conditioning Amplifier Assembly
      *h to CAN Junction Connector LH
      *i to Power Steering ECU Assembly

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      F63-1 (CANH) - F63-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Spiral cable with sensor sub-assembly (Steering sensor)
      F63-3 (CANH) - F63-14 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Smart key ECU assembly (Certification ECU)*1
      F63-4 (CANH) - F63-15 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Airbag sensor assembly
      F63-5 (CANH) - F63-16 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Radio and display receiver assembly*2
      F63-6 (CANH) - F63-17 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Power steering ECU assembly
      F63-7 (CANH) - F63-18 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Combination meter assembly
      F63-8 (CANH) - F63-19 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Air conditioning amplifier assembly
      F63-10 (CANH) - F63-21 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω CAN junction connector LH

      • *1: w/ Power Switch

      • *2: w/ Display

      Result
      Result Proceed to
      OK A
      NG (CAN junction connector LH main line) B
      NG (ECU or sensor branch line) C
      NG (Combination meter assembly main line) D

    A

    REPLACE CAN JUNCTION CONNECTOR RH

    C

    CHECK FOR SHORT IN CAN BUS LINES (ECU, SENSOR) Click here

    D

    REPAIR OR REPLACE CAN MAIN BUS LINES (COMBINATION METER ASSEMBLY - CAN J/C RH)

    B

  4. CHECK FOR SHORT IN CAN BUS LINES (CAN J/C LH (INSTRUMENT PANEL WIRE SIDE))


    1. Disconnect the CAN junction connector LH (instrument panel wire side).

    2. A004GHSE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to CAN Junction Connector LH (Instrument Panel Wire Side))
      *b to Main Body ECU (Multiplex Network Body ECU)
      *c to DLC3
      *d to CAN Junction Connector RH
      *e to Hybrid Vehicle Control ECU

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      F62-1 (CANH) - F62-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Main body ECU (Multiplex network body ECU)
      F62-3 (CANH) - F62-14 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 1 MΩ or higher DLC3
      F62-4 (CANH) - F62-15 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 1 MΩ or higher CAN junction connector RH
      F62-5 (CANH) - F62-16 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Hybrid vehicle control ECU
      Result
      Result Proceed to
      OK A
      NG (CAN junction connector RH main line) B
      NG (ECU or sensor branch line) C
      NG (DLC3 branch line) D

    B

    REPAIR OR REPLACE CAN MAIN BUS LINES (CAN J/C LH (INSTRUMENT PANEL WIRE SIDE) - CAN J/C RH)

    C

    CHECK FOR SHORT IN CAN BUS LINES (ECU, SENSOR) Click here

    D

    REPAIR OR REPLACE CAN BRANCH LINE CONNECTED TO DLC3

    A

  5. CHECK FOR SHORT IN CAN BUS LINES (CAN J/C LH (ENGINE ROOM MAIN WIRE SIDE))


    1. Disconnect the CAN junction connector LH (engine room main wire side).

    2. A004FIXE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to CAN Junction Connector LH (Engine Room Main Wire Side))
      *b to ECM
      *c to Brake Booster with Master Cylinder Assembly (Skid Control ECU)

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      A34-9 (CANH) - A34-20 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω ECM
      A34-10 (CANH) - A34-21 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Brake booster with master cylinder assembly (Skid control ECU)
      Result
      Result Proceed to
      OK A
      NG (ECM main line) B
      NG (ECU or sensor branch line) C

    A

    REPLACE CAN JUNCTION CONNECTOR LH

    B

    REPAIR OR REPLACE CAN MAIN BUS LINES (ECM - CAN J/C LH (ENGINE ROOM MAIN WIRE SIDE))

    C

  6. CHECK FOR SHORT IN CAN BUS LINES (ECU, SENSOR)


    1. Reconnect all wire harness connectors (CAN junction connector LH and CAN junction connector RH).

    2. Disconnect the connector that includes terminals CANH and CANL from the ECU (or sensor) to which the short circuited branch line is connected Click here.

    3. A004F4EE01
      Text in Illustration
      *1 DLC3

      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

      Tech Tips

      If the resistance becomes normal (between 54 and 69 Ω) when the connector is disconnected from the ECU (or sensor), there may be a short in the ECU (or sensor).


    OK

    REPLACE CORRESPONDING ECU OR SENSOR

    NG

    REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINES OR CONNECTOR