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DTC B2278 Engine Switch Circuit Malfunction: Wiring Diagram

WARNING: This page is about a different car, the 2006 Lexus IS 350. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Wiring Diagram - Engine Switch Circuit Malfunction
G04052692Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. READ VALUE OF INTELLIGENT TESTER (START SWITCH 1 and 2) 
    1. Connect the intelligent tester (with CAN VIM) to the DLC3.
    2. Turn the engine switch on (IG).
    3. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST.
    4. Check the DATA LIST for proper functioning of the start switches 1 and 2.

      Power source control ECU: 

      DATA LIST

      Item Measurement Item/Display (Range) Normal Condition Diagnostic Note
      STSW 1 Start Switch 1/ ON or OFF ON: Engine switch on (IG)
      OFF: Engine switch OFF      		 -
      STSW 2 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. 

      Result 

      RESULT CHART

      Result Proceed to
      OK (When troubleshooting according to the DTC chart) A
      OK (When troubleshooting according to the PROBLEM SYMPTOMS TABLE) B
      NG C

    B : PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE 

    C : Go to step 2 

    A : REPLACE POWER SOURCE CONTROL ECU 

  2. INSPECT ENGINE SWITCH 
    1. Remove the engine switch.
      Fig 2: Identifying Terminals Of Engine Switch
      G04052693Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance of the switch.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection 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

    NG : REPLACE ENGINE SWITCH 

    OK : GO TO NEXT STEP 

  3. CHECK WIRE HARNESS (ENGINE SWITCH - POWER SOURCE CONTROL ECU AND BODY GROUND) 
    1. Disconnect the J31 switch connector.
    2. Disconnect the J55 ECU connector.
    3. Measure the resistance of the wire harness side connectors.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection (Symbols) Specified Condition
      J31-7 (SS1) - J55-14 (SSW1) Below 1 Ω
      J31-2 (SS2) - J55-37 (SSW2) Below 1 Ω
      J31-5 (GND) - Body ground Below 1 Ω
      J31-7 (SS1) or J55-14 (SSW1) - Body ground 10 kΩ or higher
      J31-2 (SS2) or J55-37 (SSW2) - Body ground 10 kΩ or higher
      Fig 3: Identifying J31 Engine Switch Connector
      G04052694Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG : REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK : REPLACE POWER SOURCE CONTROL ECU 

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