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ECM Power Source Circuit [09/2023 - ]: Procedure

WARNING: This page is about a different car, the 2024 Lexus TX 500h. 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
      B77-9 (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 (IGP TERMINAL VOLTAGE) 
    1. Disconnect the ECM connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B77-8 (IGP) - Body ground Ignition switch ON 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 PROCEDURE - Step 3

      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 from the No. 1 engine room relay block and No. 1 junction block assembly.
    3. Remove the IGT/INJ relay, EFI-MAIN NO. 2 relay, EFI-MAIN NO. 3 relay and INV W/PMP relay from the No. 1 engine room relay block and No. 1 junction block assembly.

      HINT: 

      Remove the IGT/INJ, EFI-MAIN NO. 2, EFI-MAIN NO. 3 and INV W/PMP 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) - B77-2 (MREL) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - C27-12 (+B) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - C27-11 (+B2) Always Below 1 Ω
      5 (EFI-MAIN NO. 1 relay) - C27-10 (+B3) Always Below 1 Ω
      2 (EFI-MAIN NO. 1 relay) or B77-2 (MREL) - Body ground and other terminals Always 10 kΩ or higher
      5 (EFI-MAIN NO. 1 relay), C27-12 (+B), C27-11 (+B2) or C27-10 (+B3) - 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) 
    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.

      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 [09/2023 - ] 

    Result: 

    NG 

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

  6. INSPECT IGP NO. 1 RELAY 
    1. Inspect the IGP NO. 1 relay.

      Refer to PROCEDURE - Step 6

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE IGP NO. 1 RELAY 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (IGP NO. 1 RELAY - ECM) 
    1. Disconnect the ECM 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
      5 (IGP NO. 1 relay) - B77-8 (IGP) Always Below 1 Ω
      5 (IGP NO. 1 relay) or B77-8 (IGP) - 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 TERMINAL VOLTAGE (POWER SOURCE 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.

      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 (AUXILIARY BATTERY - IGP NO. 1 RELAY) 

    Result: 

    OK 

    See step  9

  9. 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  10

  10. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - 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 SMART ACCESS SYSTEM WITH PUSH-BUTTON START. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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