DTC    B278A    Short to GND in Immobiliser System Power Source Circuit

for Preparation Click here


DESCRIPTION

This DTC is stored when the engine switch power source supply line is open or shorted.

DTC No.
DTC Detection Condition
Trouble Area
B278A
Engine switch power source supply line is open or shorted.
  1. Wire harness or connector
  2. Engine switch
  3. Certification ECU

WIRING DIAGRAM


B151004E18


INSPECTION PROCEDURE

NOTICE:
If the certification ECU is replaced, register the key.

1.CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)

B199500E01


Text in Illustration 
*1
Front view of wire harness connector
(to Certification ECU)
*2
Front view of wire harness connector
(to Engine Switch)

  1. Disconnect the certification ECU connector.

  1. Disconnect the engine switch connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    D34-28 (VC5) -D27-14 (VC5)
    		Always
    		Below 1 Ω
    D34-36 (AGND) - D27-8 (AGND)
    		Always
    		Below 1 Ω
    D34-28 (VC5) - Body ground
    		Always
    		10 kΩ or higher
    D34-36 (AGND) - Body ground
    		Always
    		10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2.CHECK HARNESS AND CONNECTOR (ENGINE SWITCH - POWER SOURCE AND BODY GROUND)

  1. Reconnect the certification ECU connector.



    B216008E01

  1. Reconnect the engine switch connector.

  1. Using an oscilloscope, check the waveform.

    Waveform:
    Item
    		Content
    Tester Connection
    		D27-14(VC5) - D27-8(AGND)
    Tool Setting
    		2 V/DIV - 200 ms./DIV
    Condition
    		Engine switch off, key not in cabin, and 30 seconds or less after engine switch pushed.

    OK:
    Waveform is output normally (see illustration)

    Text in Illustration 
    *1
    		Component with harness connected
    (Engine Switch)



NG
REPLACE CERTIFICATION ECU
OK

REPLACE ENGINE SWITCH (Click here)