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ECM Power Source Circuit [09/2024 - ]: Procedure

WARNING: This page is about a different variant/trim than selected.
  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
      A178-22 (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.
      GTY1181073Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to ECM)

      Standard Voltage

      Tester Connection Condition Specified Condition
      A178-30 (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 

    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 (EFI-MAIN NO. 1 RELAY - ECM) 
    1. Disconnect the ECM connector.
    2. Remove the EFI-MAIN NO. 1 relay, EFI-MAIN NO. 3 relay and EDU relay from the No. 1 engine room relay block and No. 1 junction block assembly.

      HINT: 

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

    3. 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) - A178-26 (MREL) Always Below 1 Ω
      3 (EFI-MAIN NO. 1 relay) - A178-21 (+B) Always Below 1 Ω
      3 (EFI-MAIN NO. 1 relay) - A178-51 (+B2) Always Below 1 Ω
      1 (EFI-MAIN NO. 1 relay) or A178-26 (MREL) - Body ground and other terminals Always 10 kΩ or higher
      3 (EFI-MAIN NO. 1 relay), A178-21(+B) or A178-51 (+B2) - 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) 
    GTY1104117Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *1 No. 1 Engine Room Relay Block and No. 1 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 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
      2 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V
      5 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE ECM 

    Refer to REMOVAL [09/2024 - ]

    Result: 

    NG 

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

  6. INSPECT IGP-MAIN RELAY 

    Refer to ON-VEHICLE INSPECTION [11/2022 - ]

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE IGP-MAIN RELAY 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (IGP-MAIN RELAY - ECM) 
    1. Disconnect the ECM connector.
    2. Remove the IGP-MAIN 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
      3 (IGP-MAIN relay) - A178-30 (IGP) Always Below 1 Ω
      3 (IGP-MAIN relay) or A178-30 (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 HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF IGP-MAIN RELAY) 
    GTY1108347Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
    *2 IGP-MAIN Relay
    1. Remove the IGP-MAIN 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
      5 (IGP-MAIN relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - IGP-MAIN RELAY) 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (IGP-MAIN RELAY - BODY GROUND) 
    1. Remove the IGP-MAIN 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 (IGP-MAIN relay) - Body ground Always Below 1 Ω

      Result

      Result Proceed to
      OK (w/ Smart Key System) A
      OK (w/o Smart Key System) B
      NG C

    Result: 

    B 

    See step  11

    Result: 

    C 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    A 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - IGP-MAIN RELAY) 
    1. Disconnect the certification ECU (smart key ECU assembly) connector.
    2. Remove the IGP-MAIN 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
      O175-24 (IGPD) - 2 (IGP-MAIN relay) Always Below 1 Ω
      O175-24 (IGPD) or 2 (IGP-MAIN relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO SMART KEY SYSTEM 

    Refer to HOW TO PROCEED WITH TROUBLESHOOTING [11/2022 - ]

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. INSPECT IGNITION OR STARTER SWITCH ASSEMBLY 
    1. Inspect the ignition or starter switch assembly.

      Refer to INSPECTION [01/2019 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE IGNITION OR STARTER SWITCH ASSEMBLY 

    Refer to REMOVAL [01/2019 - ]

    Result: 

    OK 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (IGNITION OR STARTER SWITCH ASSEMBLY - IGP-MAIN RELAY) 
    1. Disconnect the ignition or starter switch assembly connector.
    2. Remove the IGP-MAIN 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
      I12-8 (IG1) - 2 (IGP-MAIN relay) Always Below 1 Ω
      I12-8 (IG1) or 2 (IGP-MAIN relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - IGNITION OR STARTER SWITCH ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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