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Home >> Lexus >> 2008 >> IS 250 RWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (Theft Deterrent / Keyless Entry) >> Engine Immobilizer System >> DTC B278A: Short to GND in Immobilizer System Power Source Circuit >> Inspection Procedure

Inspection Procedure

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: If the certification ECU (smart key ECU assembly) is replaced, register the key (See REGISTRATION  ).
  1. CHECK DTC OUTPUT 
    1. Clear the DTCs (See DTC CHECK / CLEAR  ).
    2. Recheck for DTCs.

      OK: B278A output does not recur. 

    NG: Go to step 2 

    OK: USE SIMULATION METHOD TO CHECK  (See HOW TO PROCEED WITH TROUBLESHOOTING )

  2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH) 
    1. Disconnect the certification ECU (smart key ECU assembly) and engine switch connectors.
    2. Measure the resistance according to the value (s) in the table below.

      Standard Resistance 

      RESISTANCE REFERENCE

      Tester Connection Condition Specified Condition
      P33-30 (VC5) - J31-14 (VC5) Always Below 1 Ω
      P33-40 (AGND) - J31-8 (AGND) Always Below 1 Ω
      P33-17 (E) - Body ground Always Below 1 Ω
      P33-30 (VC5) - Body ground Always 10 kΩ or higher
      P33-40 (AGND) - Body ground Always 10 kΩ or higher
      3. Fig 1: Identifying P33 And J31 Connector Terminal
      G05754509Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next Step 

  3. CHECK HARNESS AND CONNECTOR (ENGINE SWITCH POWER SOURCE) 
    1. Reconnect the certification ECU (smart key ECU assembly) and engine switch connectors
    2. Measure the voltage according to the value (s) in the table below.

      Standard Voltage 

      VOLTAGE SPECIFICATION

      Tester Connection Condition Specified Condition
      P33-30 (VC5) - Body ground Key is not in cabin Below 1 V
      P33-30 (VC5) - Body ground Engine switch pressed 4 6 to 5 4 V
      3. Fig 2: Identifying P33 Connector Terminal
      G05754510Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)  (See REMOVAL  )

    OK: Go to next Step 

  4. CHECK HARNESS AND CONNECTOR (ENGINE SWITCH BODY GROUND) 
    1. Measure the resistance according to the value (s) in the table below

      Standard Resistance 

      RESISTANCE REFERENCE

      Tester Connection Condition Specified Condition
      P33-40 (AGND) - Body ground Always Below 1 Ω
      2. Fig 3: Identifying P33 Connector Terminal And AGND
      G05754511Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)  (See REMOVAL  )

    OK: REPLACE ENGINE SWITCH  (See REMOVAL )

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