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

WARNING: This page is about a different car, the 2025 Toyota GR Corolla, 2024 Toyota GR Corolla, and 2023 Toyota GR Corolla. 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
      A139-10 (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
      A139-2 (IGP) - Body ground Ignition switch ON 11 to 14 V
      GTY1104391Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to ECM)

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  6

    Result: 

    OK 

    See step  3

  3. INSPECT EFI MAIN NO. 1 RELAY 

    Refer to ON-VEHICLE INSPECTION [09/2022 - ]

    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. Remove the EFI MAIN NO. 1 relay, EFI-MAIN NO. 2 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. 1 relay, EFI-MAIN NO. 2 relay, EFI-MAIN NO. 3 relay and EDU relay connected between the checked terminals as the coil inside the relay influences the measurement value.

    2. Disconnect the ECM connector.
    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) - A139-15 (MREL) Always Below 1 Ω
      5 (EFI MAIN NO. 1 relay) - A139-9 (+B) Always Below 1 Ω
      5 (EFI MAIN NO. 1 relay) - A139-35 (+B2) Always Below 1 Ω
      1 (EFI MAIN NO. 1 relay) or A139-15 (MREL) - Body ground and other terminals Always 10 kΩ or higher
      5 (EFI MAIN NO. 1 relay), A139-9 (+B) or A139-35 (+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) 
    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
      2 (EFI MAIN NO. 1 relay) - Body ground Always 11 to 14 V
      GTY1251985Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 EFI MAIN NO. 1 Relay

      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 NO. 1 INTEGRATION RELAY (IG2 NO. 1 RELAY) 

    Refer to INSPECTION [11/2022 - ]

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE NO. 1 INTEGRATION RELAY 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - ECM) 
    1. Disconnect the No. 1 integration relay connector.
    2. Disconnect the ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      9A-9 - A139-2 (IGP) Always Below 1 Ω
      9A-9 or A139-2 (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 NO. 1 INTEGRATION RELAY) 
    GTY1109327Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to No. 1 Integration Relay)
    1. Disconnect the No. 1 integration relay connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      9A-10 - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

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

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - BODY GROUND) 
    1. Disconnect the No. 1 integration relay connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      9A-8 - 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 - NO. 1 INTEGRATION RELAY) 
    1. Disconnect the certification ECU (smart key ECU assembly) connector.
    2. Disconnect the No. 1 integration relay connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      O175-22 (IGPD) - 9A-7 Always Below 1 Ω
      O175-22 (IGPD) or 9A-7 - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO SMART KEY SYSTEM (FOR START FUNCTION) 

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

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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