CAN COMMUNICATION SYSTEM (for LHD), Diagnostic DTC:U0100

DTC Code DTC Name
U0100 Lost Communication with ECM / PCM "A"

DESCRIPTION

DTC Code DTC Detection Condition Trouble Area
U0100 There is no communication from the ECM.

  • Power source or inside of ECM

  • ECM CAN main wire or connector

  • ECM

WIRING DIAGRAM

A01FF3UE02

INSPECTION PROCEDURE

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 Click here.

  • Before measuring the resistance of the CAN bus, turn the engine 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 engine 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 notice before proceeding with work Click here.

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

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

  • DTC check procedure: Drive the vehicle for 3.5 seconds or more at a speed of 60 km/h (36 mph) or more.

  • After the repair, perform 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 engine switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.

  • 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. RECONFIRM DTC OUTPUT


    1. Reconfirm DTCs.

      Tech Tips

      If DTC U1002 is output from Gateway of the network gateway ECU, this indicates a sub bus 19 malfunction. Troubleshoot for DTC U1002 and check for malfunctions in sub bus 19.

      Result
      Result Proceed to
      DTC U1002 is not output from network gateway ECU. A
      DTC U1002 is output from network gateway ECU. B

    B

    GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC Click here

    A

  2. RECONFIRM DTC OUTPUT


    1. Reconfirm DTCs.

      Tech Tips

      If DTC U1103 is output from Gateway of the network gateway ECU, this indicates a sub bus 15 malfunction. Troubleshoot for DTC U1103 and check for malfunctions in sub bus 15.

      Result
      Result Proceed to
      DTC U1103 is not output from certification ECU (smart key ECU assembly). A
      DTC U1103 is output from certification ECU (smart key ECU assembly). B

    B

    GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC Click here

    A

  3. CHECK FOR OPEN IN CAN BUS WIRE (ECM CAN MAIN WIRE)


    1. A01FGQ0E10
      Text in Illustration
      *A Sub Bus 19 (except AA81E)
      *B Sub Bus 19 (for AA81E)
      *C Sub Bus 15
      *a

      Rear view of wire harness connector

      (to ECM)

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

    2. Disconnect the ECM connector.

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

      Standard Resistance
      Sub Bus 19 (except AA81E)
      Tester Connection Condition Specified Condition
      A21-10 (CANU) - A21-9 (CAND) Cable disconnected from negative (-) battery terminal 108 to 132 Ω
      Sub Bus 19 (for AA81E)
      Tester Connection Condition Specified Condition
      A21-18 (CANU) - A21-17 (CAND) Cable disconnected from negative (-) battery terminal 108 to 132 Ω
      Sub Bus 15
      Tester Connection Condition Specified Condition
      A21-12 (CANP) - A21-11 (CANN) Cable disconnected from negative (-) battery terminal 108 to 132 Ω

    NG

    REPAIR OR REPLACE ECM CAN MAIN WIRE OR CONNECTOR (CANU, CAND, CANP, CANN)

    OK

  4. CHECK HARNESS AND CONNECTOR (ECM - BATTERY AND BODY GROUND)


    1. Connect the cable to the negative (-) battery terminal.

      A01FIMGE01
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to ECM)

      		 - -

      Note

      When connecting the cable, some systems need to be initialized after the cable is reconnected Click here.

    2. Disconnect the ECM connectors.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A19-7 (BATT) - Body ground Always 11 to 14 V
      A21-1 (+B2) - Body ground Battery positive (+) voltage applied to terminal A19-3 (MREL) 11 to 14 V
      A21-2 (+B) - Body ground Battery positive (+) voltage applied to terminal A19-3 (MREL) 11 to 14 V
      A19-8 (IGSW) - Body ground Engine switch on (IG) 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A19-1 (EC) - Body ground Always Below 1 Ω
      F2-1 (E02) - Body ground Always Below 1 Ω
      F2-2 (E01) - Body ground Always Below 1 Ω
      F2-5 (ME01) - Body ground Always Below 1 Ω
      F4-1 (E1) - Body ground Always Below 1 Ω
      Result
      Result Proceed to
      OK (for 2GR-FSE) A
      OK (for 4GR-FSE) B
      NG C

    B

    REPLACE ECM Click here

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    A

    REPLACE ECM Click here