Dtc B2278 Engine Switch Circuit Malfunction

Engine. Lexus Is250, Is220D. Gse20 Ale20
4Gr-Fse Starting. Lexus Is250, Is220D. Gse20 Ale20

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK CONNECTORS

CHECK HARNESS AND CONNECTOR (POWER SOURCE CONTROL ECU -BODY GROUND)

INSPECT ENGINE SWITCH

CHECK WIRE HARNESS (ENGINE SWITCH - POWER SOURCE CONTROL ECU AND BODY GROUND)

READ VALUE OF INTELLIGENT TESTER (START SWITCH 1 AND 2)

RECHECK FOR DTC

DTC B2278 Engine Switch Circuit Malfunction


DESCRIPTION

This DTC is output when 1) a malfunction is detected between the power source control ECU and the engine switch; or 2) either of the switches inside the engine switch is malfunctioning.
HINT:
When the power source control ECU is replaced with a new one and the negative (-) battery terminal is connected, the power source mode becomes the IG-ON mode. When the battery is removed and reinstalled, the power source mode that was selected when the battery was removed is restored.

DTC No.
DTC Detection Condition
Trouble Area
B2278
Communication is abnormal between the power source control ECU and engine switch or the engine switch is defective
  1. Engine switch
  2. Power source control ECU
  3. Wire harness or connector

WIRING DIAGRAM


Lexus Is250, Is220D. Gse20 Ale20.4Gr-Fse Starting.Starting System. Dtc B2278 Engine Switch Circuit Malfunction


INSPECTION PROCEDURE

1.CHECK CONNECTORS

  1. Check that the connectors are securely connected and the terminals are not deformed or loose.

    OK:
    The connectors are securely connected and the terminals are not deformed or loose.


NG
REPAIR OR REPLACE CONNECTORS
OK


2.CHECK HARNESS AND CONNECTOR (POWER SOURCE CONTROL ECU -BODY GROUND)


    Lexus Is250, Is220D. Gse20 Ale20.4Gr-Fse Starting.Starting System. Dtc B2278 Engine Switch Circuit Malfunction

  1. Disconnect the J55 ECU connector.

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

    Standard resistance:
    Tester Connection (Symbols)
    		Condition
    		Specified Condition
    J55-6 (GND2) - Body ground
    		Always
    		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.INSPECT ENGINE SWITCH


  1. Remove the engine switch.


    Lexus Is250, Is220D. Gse20 Ale20.4Gr-Fse Starting.Starting System. Dtc B2278 Engine Switch Circuit Malfunction

  1. Disconnect the switch connector.

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

    Standard resistance:
    Tester Connection
    (Symbols)
    		Switch Condition
    		Specified Condition
    7 (SS1) - 5 (GND)
    		Pushed
    		Below 1 Ω
    2 (SS2) - 5 (GND)
    		Pushed
    		Below 1 Ω
    7 (SS1) - 5 (GND)
    		Not pushed
    		10 kΩ or higher
    2 (SS2) - 5 (GND)
    		Not pushed
    		10 kΩ or higher
    HINT:
    This switch is a momentary type switch.


NG
REPLACE ENGINE SWITCH
OK


4.CHECK WIRE HARNESS (ENGINE SWITCH - POWER SOURCE CONTROL ECU AND BODY GROUND)


    Lexus Is250, Is220D. Gse20 Ale20.4Gr-Fse Starting.Starting System. Dtc B2278 Engine Switch Circuit Malfunction

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

    Standard resistance:
    Tester Connection (Symbols)
    		Condition
    		Specified Condition
    J31-7 (SS1) - J55-14 (SSW1)
    		Always
    		Below 1 Ω
    J31-2 (SS2) - J55-37 (SSW2)
    		Always
    		Below 1 Ω
    J31-5 (GND) - Body ground
    		Always
    		Below 1 Ω
    J31-7 (SS1) or J55-14 (SSW1) - Body ground
    		Always
    		10 kΩ or higher
    J31-2 (SS2) or J55-37 (SSW2) - Body ground
    		Always
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5.READ VALUE OF INTELLIGENT TESTER (START SWITCH 1 AND 2)

  1. Reconnect the connectors.

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Check the DATA LIST for proper functioning of the start switches 1 and 2.

    Power Source Control:
    Item
    		Measurement Item/Display (Range)
    		Normal Condition
    		Diagnostic Note
    St SW1
    		Start Switch 1/ ON or OFF
    		ON: Engine switch on (IG)
    OFF: Engine switch OFF
    		-
    St SW2
    		Start Switch 2/ ON or OFF
    		ON: Engine switch on (IG)
    OFF: Engine switch OFF
    		-
    OK:
    ON (engine switch on (IG)) and OFF (engine switch off) appear on the screen.


NG
REPLACE POWER SOURCE CONTROL ECU
OK


6.RECHECK FOR DTC

  1. Delete the DTCs (Click here).

  1. Check for DTCs again.

    OK:
    DTC B2278 is not output.


NG
REPLACE POWER SOURCE CONTROL ECU
OK

CHECK INTERMITTENT PROBLEMS