DTC    U0100    Lost Communication with ECM / PCM

for Preparation Click here


DESCRIPTION


DTC No.
DTC Detection Condition
Trouble Area
U0100
No communication from the ECM continues.
  1. ECM main line or connector
  2. Power source circuit of ECM
  3. ECM

HINT:
This diagnosis procedure is for when DTC U0100 is output by the power management control ECU (Intelligent tester display: PM2 Gateway).


WIRING DIAGRAM


C234513E01


INSPECTION PROCEDURE

NOTICE:
  1. Turn the power switch off before measuring the resistances between CAN main bus lines and between CAN branch lines.
  2. Turn the power switch off before inspecting CAN bus lines for a ground short.
  3. After the power switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.
  4. 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.

HINT:
  1. 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.
  2. 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.

1.RECONFIRM DTC OUTPUT

  1. Reconfirm DTCs.

    HINT:
    If DTC U1002 is output from PM2 Gateway of the power management control ECU, this indicates a power management bus malfunction. Troubleshoot for DTC U1002 and check for malfunctions in the power management bus.

    Result:
    Result
    		Proceed to
    U1002 is not output from power management control ECU (Intelligent tester display/PM2 Gateway)
    		A
    U1002 is output from power management control ECU (Intelligent tester display/PM2 Gateway)
    		B



B
GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC (Click here)
A


2.CHECK CAN BUS LINE FOR DISCONNECTION (ECM - POWER MANAGEMENT BUS)

  1. Turn the power switch off.



    A192807E57

  1. Disconnect the ECM connector.

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

    Standard Resistance:
    Tester Connection
    		Switch Condition
    		Specified Condition
    A60-12 (CANP) - A60-4 (CANN)
    		Power switch off
    		108 to 132 Ω

    Text in Illustration 
    *a
    		Front view of wire harness connector
    (to ECM)



NG
REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (ECM MAIN LINE)
OK


3.CHECK ECM POWER SOURCE CIRCUIT

  1. Check the ECM power source circuit (Click here).



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
OK

REPLACE ECM (Click here)