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HOMESERVICE MANUALSLEXUS2010LS 460L AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ELECTRICALSTARTERSMART ACCESS SYSTEM (KEYLESS START) (DIAGNOSTIC CODES & SYMPTOM TESTS)SMART ACCESS SYSTEM WITH PUSH-BUTTON STARTDTC B2278: ENGINE SWITCH CIRCUIT MALFUNCTIONPROCEDURE
2010 Lexus LS 460L AWD

DTC B2278: Engine Switch Circuit Malfunction: Procedure

2010 Lexus LS 460L AWDSECTION Procedure
  1. READ VALUE USING TECHSTREAM (ENGINE SWITCH) 
    1. Use the Data List to check if the engine switch is functioning properly.
      MAIN BODY

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

      OK

      ON appears on the screen.

    NG → See step   3 

    OK: Go to next step 

  2. CHECK ENGINE SWITCH (SWITCH CONDITION) 
    1. Ensure the key is inside the cabin.
    2. Check that the power source mode changes as shown below each time the engine switch is pushed.

      OK

      off → on (ACC) → on (IG) → off

    NG → See step   5 

    OK → SYSTEM IS OK 

  3. INSPECT ENGINE SWITCH 
    Fig 1: Identifying Connector Terminals Of Engine Switch
    GTY259773Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the engine switch. Refer to REMOVAL .
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      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 → See step   6 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (ENGINE SWITCH - MAIN BODY ECU AND BODY GROUND) 
    Fig 2: Identifying Connector Terminals Of L36 Engine Switch And L13 Main Body ECU
    GTY288219Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the L36 engine switch connector.
    2. Disconnect the L13 main body ECU connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      L36-7 (SS1) - L13-17 (SSW1) Always Below 1 Ω
      L36-2 (SS2) - L13-16 (SSW2) Always Below 1 Ω
      L36-5 (GND) - Body ground Always Below 1 Ω
      L36-7 (SS1) or L13-17 (SSW1) - Body ground Always 10 kΩ or higher
      L36-2 (SS2) or L13-16 (SSW2) - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK → REPLACE MAIN BODY ECU 

  5. GO TO POWER SOURCE MODE DOES NOT CHANGE. Refer to  Power Source Mode does not Change  
  6. REPLACE ENGINE SWITCH. Refer to  REMOVAL 
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.