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ECM Power Source Circuit [12/2023 - ]: Procedure

WARNING: This page is about a different car, the 2024 Lexus TX 550h+. However, it is still accessible from the selected car via links, so may be relevant.
  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
      C86-53 (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 HARNESS AND CONNECTOR (IGP TERMINAL VOLTAGE) 
    1. Disconnect the ECM connector.
    2. Turn the ignition switch ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B86-4 (IGP) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  3

  3. INSPECT EFI-MAIN NO. 1 RELAY 

    Refer to PROCEDURE - Step 1

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE EFI-MAIN NO. 1 RELAY 

    Result: 

    OK 

    See step  4

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

      HINT: 

      Remove the EFI-MAIN No. 2 relay and A/F HTR relay connected between the checked terminals as the coil inside the relay influences the measurement value.

    3. Remove the EFI-MAIN NO. 2 relay from the No. 2 luggage room relay block and junction block assembly.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B86-46 (MREL) - 2 (EFI-MAIN NO. 1 relay) Always Below 1 Ω
      B86-2 (+B) - 5 (EFI-MAIN NO. 1 relay) Always Below 1 Ω
      B86-3 (+B2) - 5 (EFI-MAIN NO. 1 relay) Always Below 1 Ω
      B86-46 (MREL) or 2 (EFI-MAIN NO. 1 relay) - Body ground and other terminals Always 10 kΩ or higher
      B86-2 (+B) or 5 (EFI-MAIN NO. 1 relay) - Body ground and other terminals Always 10 kΩ or higher
      B86-3 (+B2) or 5 (EFI-MAIN NO. 1 relay) - 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 HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF EFI-MAIN NO. 1 RELAY) 
    1. Remove the EFI-MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Measure the voltage according to the value(s) in the table below.
      GTY1239641Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 EFI-MAIN NO. 1 Relay

      Standard Voltage

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

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 1 RELAY - BODY GROUND) 
    1. Remove the EFI-MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      1 (EFI-MAIN NO. 1 relay) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [12/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  7. INSPECT IGP NO. 1 RELAY 

    Refer to PROCEDURE - Step 5

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE DRIVER SIDE JUNCTION BLOCK ASSEMBLY (IGP-MAIN RELAY) 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (ECM - IGP NO. 1 RELAY) 
    1. Disconnect the ECM connector.
    2. Remove the IGP NO. 1 relay from No. 1 engine room relay block and No. 1 junction block assembly.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B86-4 (IGP) - 5 (IGP NO. 1 relay) Always Below 1 Ω
      B86-4 (IGP) or 5 (IGP NO. 1 relay) - 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  9

  9. CHECK HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF IGP NO. 1 RELAY) 
    1. Remove the IGP NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Measure the voltage according to the value(s) in the table below.
      GTY1232064Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 IGP NO. 1 Relay

      Standard Voltage

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

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (IGP NO. 1 RELAY - BODY GROUND) 
    1. Remove the IGP NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (IGP NO. 1 relay) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  11

  11. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - IGP NO. 1 RELAY) 
    1. Disconnect the certification ECU (smart key ECU assembly) connector.
    2. Remove the IGP NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B7-24 (IGPD) - 1 (IGP NO. 1 relay) Always Below 1 Ω
      B7-24 (IGPD) or 1 (IGP NO. 1 relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO ENTRY AND START SYSTEM (FOR START FUNCTION). Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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