CAN COMMUNICATION SYSTEM, Diagnostic DTC:U0100

DTC Code DTC Name
U0100 Lost Communication with ECM / PCM

DESCRIPTION

DTC No. DTC Detection Condition Trouble Area
U0100 No communication from the ECM continues.

  • ECM main wire or connector

  • Power source circuit of ECM

  • ECM

Tech Tips

The diagnosis procedure is for when DTC U0100 is output by the power management control ECU (Intelligent tester display: Power Management2).

WIRING DIAGRAM

A01JBS0E03

INSPECTION PROCEDURE

Note


  • Turn the power switch off before measuring the resistances between CAN bus main wires and between CAN bus branch wires.

  • Turn the power switch off before inspecting CAN bus wires for a ground short.

  • After the power switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.

  • Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the power switch, any other switches or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.

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. RECONFIRM DTC OUTPUT


    1. Reconfirm DTCs.

      Tech Tips

      If CAN power management bus DTC U1002 is output from the power management control ECU (Intelligent tester display/Power Management2), troubleshoot for U1002 and check for malfunctions in the power management main bus circuit.

      Result
      Result Proceed to
      U1002 is not output from power management control ECU (Intelligent tester display/Power Management2) A
      U1002 is output from power management control ECU (Intelligent tester display/Power Management2) B

    B

    REPAIR CIRCUITS INDICATED BY OUTPUT DTCS Click here

    A

  2. CHECK CAN BUS WIRE FOR DISCONNECTION (ECM MAIN WIRE/POWER MANAGEMENT BUS)


    1. Turn the power switch off.

    2. A01JCO3E25
      Text in Illustration
      *1

      Front view of wire harness connector

      (to ECM)

      Disconnect the ECM connector.

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

      Standard Resistance
      Tester Connection Switch Condition Specified Condition
      A57-12 (CANP) - A57-4 (CANN) Power switch off 108 to 132 Ω

    NG

    REPAIR OR REPLACE CAN BUS MAIN WIRE OR CONNECTOR (ECM MAIN WIRE)

    OK

  3. CHECK ECM POWER SOURCE CIRCUIT


    1. Check for the ECM power source circuit Click here.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

    OK

    REPLACE ECM Click here