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DTC    B278C    Lost Communication with Power Source Control

for Preparation Click here


DESCRIPTION

This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and power management control ECU stops for 10 seconds or more.

DTC No.
DTC Detection Condition
Trouble Area
B278C
No communication between the certification ECU (smart key ECU assembly) and power management control ECU for 10 seconds or more.
  1. Power management control ECU
  2. Certification ECU (smart key ECU assembly)
  3. Wire harness or connector
  4. AM2 fuse

WIRING DIAGRAM


B228566E02


INSPECTION PROCEDURE

NOTICE:
  1. Inspect the fuses for circuits related to this system before performing the following inspection procedure.
  2. If the certification ECU (smart key ECU assembly) is replaced, register the key.
  3. When using the intelligent tester to troubleshoot with the power switch off:
    Connect the intelligent tester to the DLC3, and turn the courtesy switch on and off at 1.5-second intervals until communication between the intelligent tester and vehicle begins.

1.CHECK HARNESS AND CONNECTOR (POWER MANAGEMENT CONTROL ECU - BATTERY AND BODY GROUND)


    B228564E02

  1. Disconnect the L5 and L6 power management control ECU connectors.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    L5-6 (E1) - Body ground
    		Always
    		Below 1 Ω

    Standard Voltage:
    Tester Connection
    		Condition
    		Specified Condition
    L5-1 (AM22) - Body ground
    		Power switch off
    		11 to 14 V
    L6-7 (AM21) - Body ground
    		Power switch off
    		11 to 14 V

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to Power Management Control ECU)



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2.CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - POWER MANAGEMENT CONTROL ECU)


    B228562E04

  1. Disconnect the L62 certification ECU (smart key ECU assembly) connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    L62-29 (LIN) - L6-11 (LIN2)
    		Always
    		Below 1 Ω
    L62-29 (LIN) - Body ground
    		Always
    		10 kΩ or higher

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to Certification ECU (Smart Key ECU Assembly))
    *2
    		Front view of wire harness connector
    (to Power Management Control ECU)



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.REPLACE POWER MANAGEMENT CONTROL ECU

  1. Replace the power management control ECU (Click here).


NEXT


4.CHECK DTC OUTPUT

  1. Clear the DTC (Click here).

  1. Recheck for DTCs.

    OK:
    DTC B278C is not output.



NG
REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)
OK

END (POWER MANAGEMENT CONTROL ECU WAS DEFECTIVE)