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Home >> Toyota >> 2025 >> Prius Plug-In Hybrid SE >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (Hybrid Control System (HEV) - Diagnostic Codes (4 Of 4) & Circuit Tests) >> HYBRID CONTROL SYSTEM (for M20A-FXS) >> ECU Power Source Circuit [12/2022 - ] >> Procedure

ECU Power Source Circuit [12/2022 - ]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. CHECK HYBRID VEHICLE CONTROL ECU (+B1 VOLTAGE) 
    1. Turn the ignition switch to ON.
    2. Measure the voltage according to the value(s) in the table below.
      GTY1154633Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Hybrid Vehicle Control ECU)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      K11-8 (+B1) - Body ground Ignition switch ON 11 to 14 V
    3. Turn the ignition switch off.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  3

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - BODY GROUND) 
    1. Disconnect the hybrid vehicle control ECU connectors.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A57-12 (E01) - Body ground Always Below 1 Ω
      A57-24 (E12) - Body ground Always Below 1 Ω
      K11-1 (E1) - Body ground Always Below 1 Ω
    3. Reconnect the hybrid vehicle control ECU connectors.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO PROBLEM SYMPTOMS TABLE 

    Refer to PROBLEM SYMPTOMS TABLE [12/2022 - ]

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  3. CHECK HYBRID VEHICLE CONTROL ECU (MREL TERMINAL VOLTAGE) 
    1. Turn the ignition switch to ON.
    2. Measure the voltage according to the value(s) in the table below.
      GTY1150119Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Hybrid Vehicle Control ECU)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      K11-10 (MREL) - Body ground Ignition switch ON 11 to 14 V
    3. Turn the Ignition switch off.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE HYBRID VEHICLE CONTROL ECU 

    Refer to REMOVAL [12/2022 - 03/2023] , or refer to REMOVAL [03/2023 - ]

    Result: 

    OK 

    See step  4

  4. CHECK FUSE (PM-IGCT) 
    1. Remove the PM-IGCT fuse 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
      PM-IGCT fuse Always Below 1 Ω
    3. Install the PM-IGCT fuse.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  5

  5. CHECK FUSE (IGCT-MAIN NO. 1) 
    1. Remove the IGCT-MAIN NO. 1 fuse 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
      IGCT-MAIN NO. 1 fuse Always Below 1 Ω
    3. Install the IGCT-MAIN NO. 1 fuse.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  12

    Result: 

    OK 

    See step  6

  6. INSPECT RELAY (IGCT-MAIN NO. 1) 
    1. Remove the IGCT-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.
      GTY1104539Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 IGCT-MAIN NO. 1 Relay

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 - 5 Auxiliary battery voltage not applied between terminals 1 and 2 10 kΩ or higher
      Auxiliary battery voltage applied between terminals 1 and 2 Below 1 Ω
    3. Install the IGCT-MAIN NO. 1 relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE RELAY (IGCT-MAIN NO. 1) 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Disconnect the hybrid vehicle control ECU connector.
    2. Remove the PM-IGCT fuse 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
      K11-8 (+B1) - 2 (PM-IGCT fuse holder) Always Below 1 Ω
    4. Install the PM-IGCT fuse.
    5. Reconnect the hybrid vehicle control ECU connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-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
      5 (IGCT-MAIN NO. 1 relay holder) - 2 (IGCT-MAIN NO. 1 fuse holder) Always Below 1 Ω
      3 (IGCT-MAIN NO. 1 relay holder) - 1 (PM-IGCT fuse holder) Always Below 1 Ω
    3. Install the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Disconnect the hybrid vehicle control ECU connector.
    2. Remove the IGCT-MAIN 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
      K11-10 (MREL) - 1 (IGCT-MAIN NO. 1 relay holder) Always Below 1 Ω
      K11-10 (MREL) or 1 (IGCT-MAIN NO. 1 relay holder) - Body ground and other terminals Always 10 kΩ or higher
    4. Install the IGCT-MAIN NO. 1 relay.
    5. Reconnect the hybrid vehicle control ECU connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - BODY GROUND) 
    1. Remove the IGCT-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
      2 (IGCT-MAIN NO. 1 relay holder) - Body ground Always Below 1 Ω
    3. Install the IGCT-MAIN NO. 1 relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    CHECK FOR INTERMITTENT PROBLEMS 

    Refer to HOW TO PROCEED WITH TROUBLESHOOTING [12/2022 - ]

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the PM-IGCT fuse from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Disconnect the hybrid vehicle control ECU connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      K11-8 (+B1) or 2 (PM-IGCT fuse holder) - Body ground and other terminals Always 10 kΩ or higher
    4. Reconnect the hybrid vehicle control ECU connector.
    5. Install the PM-IGCT fuse.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FUSE (PM-IGCT) 

    Result: 

    NG 

    See step  13

  12. CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-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
      5 (IGCT-MAIN NO. 1 relay holder) or 2 (IGCT-MAIN NO. 1 fuse holder) - Body ground and other terminals Always 10 kΩ or higher
      3 (IGCT-MAIN NO. 1 relay holder) or 1 (PM-IGCT fuse holder) - Body ground and other terminals Always 10 kΩ or higher
    3. Install the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FUSE (IGCT-MAIN NO. 1) 

    Result: 

    NG 

    See step  14

  13. REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result

    Proceed to
    NEXT

    Result: 

    NEXT 

    REPLACE FUSE (PM-IGCT) 

  14. REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result

    Proceed to
    NEXT

    Result: 

    NEXT 

    REPLACE FUSE (IGCT-MAIN NO. 1) 

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