CAN COMMUNICATION SYSTEM 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

  • Combination meter assembly

  • Radio and display receiver assembly*

  • Air conditioning amplifier assembly

  • Power steering ECU assembly

  • Certification ECU (Smart key ECU assembly)

  • Transmission control ECU assembly

  • Airbag sensor assembly

  • Power management control ECU

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

  • Main body ECU (Multiplex network body ECU)

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

  • ECM

  • No. 1 CAN junction connector

  • No. 2 CAN junction connector

  • No. 3 CAN junction connector

*: for Radio and display type

WIRING DIAGRAM

A01G2UEE01
A01G2VWE01

CAUTION / NOTICE / HINT

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.

  • 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.

    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 power switch on (IG) and 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 the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed.

    Click here

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.

  • 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.

PROCEDURE


  1. CHECK FOR SHORT IN CAN BUS LINES (COMBINATION METER ASSEMBLY - NO. 2 CAN JUNCTION CONNECTOR)


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

    2. Disconnect the E46 combination meter assembly connector.

    3. A01G2T0C27
      *a

      Front view of wire harness connector

      (to Combination Meter Assembly)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      E46-32 (CANH) - E46-31 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
      Result
      Result
      OK
      NG

    OK

    REPLACE COMBINATION METER ASSEMBLY Click here

    NG

  2. CHECK FOR SHORT IN CAN BUS LINES (ECM - NO. 1 CAN JUNCTION CONNECTOR)


    1. Reconnect the E46 combination meter assembly connector.

    2. Disconnect the A142 ECM connector.

    3. A01G2SLC08
      *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
      A142-13 (CANH) - A142-26 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
      Result
      Result
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

  3. CHECK FOR SHORT IN CAN BUS LINES (NO. 2 CAN JUNCTION CONNECTOR)


    1. Reconnect the A142 ECM connector.

    2. Disconnect the E118 No. 2 CAN junction connector.

    3. A01G3KPC37
      *a

      Front view of wire harness connector

      (to No. 2 CAN Junction Connector)
      *b to No. 3 CAN Junction Connector
      *c to Airbag Sensor Assembly
      *d to Power Steering ECU Assembly
      *e to Certification ECU (Smart Key ECU Assembly)
      *f to Combination Meter Assembly
      *g to Power Management Control ECU
      *h to Radio and Display Receiver Assembly*
      *i to Air Conditioning Amplifier Assembly
      *j to Transmission Control ECU Assembly

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      E118-1 (CANH) - E118-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω No. 3 CAN junction connector
      E118-2 (CANH) - E118-13 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Airbag sensor assembly
      E118-5 (CANH) - E118-16 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Power steering ECU assembly
      E118-6 (CANH) - E118-17 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Certification ECU (Smart key ECU assembly)
      E118-7 (CANH) - E118-18 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Combination meter assembly
      E118-8 (CANH) - E118-19 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Power management control ECU
      E118-9 (CANH) - E118-20 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Radio and display receiver assembly*
      E118-10 (CANH) - E118-21 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Air conditioning amplifier assembly
      E118-11 (CANH) - E118-22 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Transmission control ECU assembly

      *: for Radio and display type

      Result
      Result Proceed to
      OK A
      NG (No. 3 CAN junction connector main line) B
      NG (ECU or sensor branch line) C
      NG (Combination meter assembly main line) D

    A

    REPLACE NO. 2 CAN JUNCTION CONNECTOR

    C

    GO TO STEP 6 Click here

    D

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (COMBINATION METER ASSEMBLY - NO. 2 CAN JUNCTION CONNECTOR)

    B

  4. CHECK FOR SHORT IN CAN BUS LINES (NO. 1 CAN JUNCTION CONNECTOR)


    1. Reconnect the E118 No. 2 CAN junction connector.

    2. Disconnect the A32 No. 1 CAN junction connector.

    3. A01G3KPC55
      *a

      Front view of wire harness connector

      (to No. 1 CAN Junction Connector)
      *b to Skid Control ECU (Brake Booster with Master Cylinder Assembly)
      *c to ECM
      *d to No. 3 CAN Junction Connector

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      A32-9 (CANH) - A32-20 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Skid control ECU (Brake booster with master cylinder assembly)
      A32-10 (CANH) - A32-21 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω ECM
      A32-11 (CANH) - A32-22 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω No. 3 CAN junction connector
      Result
      Result Proceed to
      OK A
      NG (No. 3 CAN junction connector main line) B
      NG (ECU or sensor branch line) C
      NG (ECM main line) D

    A

    REPLACE NO. 1 CAN JUNCTION CONNECTOR

    C

    GO TO STEP 6 Click here

    D

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (ECM - NO. 1 CAN JUNCTION CONNECTOR)

    B

  5. CHECK FOR SHORT IN CAN BUS LINES (NO. 3 CAN JUNCTION CONNECTOR)


    1. Resconnect the A32 No. 1 CAN junction connector.

    2. Disconnect the E119 No. 3 CAN junction connector.

    3. A01G3KPC56
      *a

      Front view of wire harness connector

      (to No. 3 CAN Junction Connector)
      *b to No. 1 CAN Junction Connector
      *c to DLC3
      *d to Steering Sensor (Spiral Cable with Sensor Sub-assembly)
      *e to Main Body ECU (Multiplex Network Body ECU)
      *f to No. 2 CAN Junction Connector

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      E119-1 (CANH) - E119-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω No. 1 CAN junction connector
      E119-2 (CANH) - E119-13 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 1 MΩ or higher DLC3
      E119-3 (CANH) - E119-14 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Steering sensor (Spiral cable with sensor sub-assembly)
      E119-4 (CANH) - E119-15 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Main body ECU (Multiplex network body ECU)
      E119-5 (CANH) - E119-16 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω No. 2 CAN junction connector
      Result
      Result Proceed to
      OK A
      NG (No. 1 CAN junction connector main line) B
      NG (No. 2 CAN junction connector main line) C
      NG (ECU or sensor branch line) D
      NG (DLC3 branch line) E

    A

    REPLACE NO. 3 CAN JUNCTION CONNECTOR

    B

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 1 CAN JUNCTION CONNECTOR - NO. 3 CAN JUNCTION CONNECTOR)

    C

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 2 CAN JUNCTION CONNECTOR - NO. 3 CAN JUNCTION CONNECTOR)

    E

    REPAIR OR REPLACE CAN BRANCH LINE CONNECTED TO DLC3

    D

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


    1. Reconnect all wire harness connectors (No. 1 CAN junction connector, No. 2 CAN junction connector and No. 3 CAN junction connector).

    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. A01G2MXC20
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      E11-6 (CANH) - E11-14 (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).

      Result
      Result
      OK
      NG

    OK

    REPLACE CORRESPONDING ECU OR SENSOR

    NG

    REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINES OR CONNECTOR