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Home >> Lexus >> 2019 >> LS 500 Base, AWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System - Diagnostic Codes (14 Of 14), Circuit Tests & Symptom Tests (1 Of 4) >> SFI System >> ECM Power Source Circuit [12/2017 - 10/2020] >> Procedure

ECM Power Source Circuit [12/2017 - 10/2020]: Procedure

  1. CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND) 
    1. Disconnect the ECM connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A95-9 (E1) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  2

  2. CHECK TERMINAL VOLTAGE (IGSW TERMINAL VOLTAGE) 
    1. Disconnect the ECM connector.
    2. Turn the engine switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A95-8 (IGSW) - Body ground Engine switch on (IG) 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  6

    Result: 

    OK 

    See step  3

  3. INSPECT EFI-MAIN NO. 1 RELAY 
    1. Inspect the EFI-MAIN NO. 1 relay.

      Refer to ON-VEHICLE INSPECTION [12/2017 - 10/2023]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE EFI-MAIN NO. 1 RELAY 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 1 RELAY - ECM) 
    1. Disconnect the ECM connector.
    2. Remove the EFI-MAIN NO. 1 relay and EFI-MAIN NO. 3 relay from the No. 1 engine room relay block and junction block assembly.
    3. Remove the EFI-MAIN NO. 2 relay from the No. 2 luggage room relay block and junction block assembly.

      HINT: 

      Remove the EFI-MAIN NO. 2 and EFI-MAIN NO. 3 relays connected between the checked terminals as the coil inside the relay influences the measurement value.

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (EFI-MAIN NO. 1 relay) - A95-2 (MREL) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - D2-12 (+B) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - D2-11 (+B2) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - D2-10 (+B3) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - D2-9 (+B4) Always Below 1 Ω
      2 (EFI-MAIN NO. 1 relay) or A95-2 (MREL) - Body ground and other terminals Always 10 kΩ or higher
      5 (EFI-MAIN NO. 1 relay), D2-12 (+B), D2-11 (+B2), D2-10 (+B3) or D2-9 (+B4) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI-MAIN NO. 1 RELAY) 
    GTY814836Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *1 No. 1 Engine Room Relay Block and Junction Block Assembly
    *2 EFI-MAIN NO. 1 Relay
    1. Remove the EFI-MAIN NO. 1 relay from the No. 1 engine room relay block and junction block assembly.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      3 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V
      1 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [12/2017 - 09/2018]  , or refer to  REMOVAL [09/2018 - 10/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - EFI-MAIN NO. 1 RELAY) 

  6. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (IG2 D RELAY) 
    1. Inspect the IG2 D relay.

      Refer to Power Source Mode does not Change to ON (IG) [12/2017 - 10/2023]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (IG2 D RELAY) 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (IG2D RELAY - ECM) 
    1. Disconnect the ECM connector.
    2. Disconnect the instrument panel junction block assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      5F-1 - A95-8 (IGSW) Always Below 1 Ω
      5F-1 or A95-8 (IGSW) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF IG2 D RELAY) 
    1. Disconnect the instrument panel junction block assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      5L-1 - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (IG2 D RELAY - BODY GROUND) 
    1. Disconnect the instrument panel junction block assembly connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      5D-6 - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - IG2 D RELAY) 
    1. Disconnect the certification ECU (smart key ECU assembly) connector.
    2. Disconnect the instrument panel junction block assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      G71-17 (IG1D) - 5D-18 Always Below 1 Ω
      G71-17 (IG1D) or 5D-18 - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START (FOR START FUNCTION). Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 10/2022] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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