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Home >> Toyota >> 2021 >> Mirai Limited >> Repair and Diagnosis >> Hybrid/Electric Powertrain >> Testing and Diagnosis >> Hybrid Control System - Diagnostic Codes (18 Of 18) & Circuit Tests (1 Of 3) >> Hybrid Control System >> ECU Power Source Circuit [11/2020 - 12/2023] >> Procedure

ECU Power Source Circuit [11/2020 - 12/2023]: Procedure

  1. CHECK EV CONTROL ECU (+B1, +B2 VOLTAGE) 
    1. Turn the ignition switch to ON (IG).
    2. Measure the voltage according to the value(s) in the table below.
      GTY1003996Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (EV Control ECU)

      Standard Voltage

      Tester Connection Condition Specified Condition
      A17-1 (+B1) - Body ground Ignition switch ON 11 to 14 V
      A8-7 (+B2) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG
    3. Turn the ignition switch off.

    Result: 

    NG 

    See step  3

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (EV CONTROL ECU - BODY GROUND) 
    1. Disconnect the A8 and A17 EV control ECU connectors.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A17-4 (E1) - Body ground Ignition switch off Below 1 Ω
      A8-4 (E12) - Body ground Ignition switch off Below 1 Ω
      A17-3 (E01) - Body ground Ignition switch off Below 1 Ω
      A8-5 (E02) - Body ground Ignition switch off Below 1 Ω
      GTY1003508Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Rear view of wire harness connector
      (to EV Control ECU)

      Result

      Proceed to
      OK
      NG
    3. Reconnect the A8 and A17 EV control ECU connectors.

    Result: 

    OK 

    GO TO PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [11/2020 - 12/2023] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  3. CHECK EV CONTROL ECU (MREL VOLTAGE) 
    1. Turn the ignition switch to ON (IG).
    2. Measure the voltage according to the value(s) in the table below.
      GTY1003998Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (to EV Control ECU)

      Standard Voltage

      Tester Connection Condition Specified Condition
      A8-21 (MREL) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG
    3. Turn the ignition switch off.

    Result: 

    NG 

    REPLACE EV CONTROL ECU. Refer to  REMOVAL [11/2020 - 11/2021]  , or refer to  REMOVAL [11/2021 - 12/2022]  , or refer to  REMOVAL [12/2022 - 12/2023] 

    Result: 

    OK 

    See step  4

  4. CHECK FUSE (PM-IGCT) 
    1. Remove the PM-IGCT fuse from the luggage room relay block.
      GTY1002912Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      PM-IGCT fuse terminals Always Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Install the PM-IGCT fuse.

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  5

  5. CHECK FUSE (IGCT NO. 2) 
    1. Remove the IGCT NO. 2 fuse from the luggage room relay block.
      GTY1003393Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 IGCT NO. 2 Fuse
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      IGCT NO. 2 fuse terminals Always Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Install the IGCT NO. 2 fuse.

    Result: 

    NG 

    See step  12

    Result: 

    OK 

    See step  6

  6. INSPECT RELAY (IGCT NO. 2) 
    1. Remove the IGCT NO. 2 relay from the luggage room relay block.
      GTY1004095Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 IGCT NO. 2 Relay
    2. Measure the resistance according to the value(s) in the table below.
      GTY1005390Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 IGCT NO. 2 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

      Result

      Proceed to
      OK
      NG
    3. Install the IGCT NO. 2 relay.

    Result: 

    NG 

    REPLACE RELAY (IGCT NO. 2) 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (EV CONTROL ECU - LUGGAGE ROOM RELAY BLOCK) 
    1. Disconnect the A8 and A17 EV control ECU connector.
    2. Remove the PM-IGCT fuse from the luggage room relay block.
      GTY1002914Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
    3. Measure the resistance according to the value(s) in the table below.
      GTY1003298Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block *2 PM-IGCT Fuse
      *a Rear view of wire harness connector
      (to EV Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A17-1 (+B1) - 2 (PM-IGCT fuse holder) Ignition switch off Below 1 Ω
      A8-7 (+B2) - 2 (PM-IGCT fuse holder) Ignition switch off Below 1 Ω

      Result

      Proceed to
      OK
      NG
    4. Reconnect the A8 and A17 EV control ECU connector.
    5. Install the PM-IGCT fuse.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (LUGGAGE ROOM RELAY BLOCK) 
    1. Remove the IGCT NO. 2 fuse, PM-IGCT fuse and IGCT NO. 2 relay from the luggage room relay block.
      GTY1003838Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
      *3 IGCT NO. 2 Fuse
      *4 IGCT NO. 2 Relay
    2. Measure the resistance according to the value(s) in the table below.
      GTY1003349Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
      *3 IGCT NO. 2 Fuse
      *4 IGCT NO. 2 Relay

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 (IGCT NO. 2 relay holder) - 2 (IGCT NO. 2 fuse holder) Ignition switch off Below 1 Ω
      5 (IGCT NO. 2 relay holder) - 1 (PM-IGCT fuse holder) Ignition switch off Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Install the IGCT NO. 2 fuse, PM-IGCT fuse and IGCT NO. 2 relay.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (EV CONTROL ECU - LUGGAGE ROOM RELAY BLOCK) 
    1. Disconnect the A8 EV control ECU connector.
    2. Remove the IGCT NO. 2 relay from the luggage room relay block.
      GTY1004094Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 IGCT NO. 2 Relay
    3. Measure the resistance according to the value(s) in the table below.
      GTY1003695Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block *2 IGCT NO. 2 Relay
      *a Rear view of wire harness connector
      (to EV Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A8-21 (MREL) - 2 (IGCT NO. 2 relay holder) Ignition switch off Below 1 Ω
      A8-21 (MREL) or 2 (IGCT NO. 2 relay holder) - Body ground and other terminals Ignition switch off 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Install the IGCT NO. 2 relay.
    5. Reconnect the A8 EV control ECU connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (LUGGAGE ROOM RELAY BLOCK - BODY GROUND) 
    1. Remove the IGCT NO. 2 relay from the luggage room relay block.
      GTY1004099Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 IGCT NO. 2 Relay
    2. Measure the resistance according to the value(s) in the table below.
      GTY1003198Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 IGCT NO. 2 Relay

      Standard Resistance

      Tester Connection Condition Specified Condition
      1 (IGCT NO. 2 relay holder) - Body ground Ignition switch off Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Install the IGCT NO. 2 relay.

    Result: 

    OK 

    CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [11/2020 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. CHECK HARNESS AND CONNECTOR (EV CONTROL ECU - LUGGAGE ROOM RELAY BLOCK) 
    1. Remove the PM-IGCT fuse from the luggage room relay block.
      GTY1002913Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
    2. Disconnect the A8 and A17 EV control ECU connector.
    3. Measure the resistance according to the value(s) in the table below.
      GTY1003295Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block *2 PM-IGCT Fuse
      *a Rear view of wire harness connector
      (to EV Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A17-1 (+B1) or 2 (PM-IGCT fuse holder) - Body ground and other terminals Ignition switch off 10 kΩ or higher
      A8-7 (+B2) or 2 (PM-IGCT fuse holder) - Body ground and other terminals Ignition switch off 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Reconnect the A8 and A17 EV control ECU connector.
    5. Install the PM-IGCT fuse.

    Result: 

    OK 

    REPLACE FUSE (PM-IGCT) 

    Result: 

    NG 

    See step  13

  12. CHECK HARNESS AND CONNECTOR (LUGGAGE ROOM RELAY BLOCK) 
    1. Disconnect the IGCT NO. 2 fuse, PM-IGCT fuse and IGCT NO. 2 relay from the luggage room relay block.
      GTY1003838Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
      *3 IGCT NO. 2 Fuse
      *4 IGCT NO. 2 Relay
    2. Measure the resistance according to the value(s) in the table below.
      GTY1003350Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Luggage Room Relay Block
      *2 PM-IGCT Fuse
      *3 IGCT NO. 2 Fuse
      *4 IGCT NO. 2 Relay
      STANDARD RESISTANCE:

      Tester Connection Condition Specified Condition
      3 (IGCT NO. 2 relay holder) or 2 (IGCT NO. 2 fuse holder) - Body ground and other terminals Ignition switch off 10 kΩ or higher
      5 (IGCT NO. 2 relay holder) or 1 (PM-IGCT fuse holder) - Body ground and other terminals Ignition switch off 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    3. Install the IGCT NO. 2 fuse, PM-IGCT fuse and IGCT NO. 2 relay.

    Result: 

    OK 

    REPLACE FUSE (IGCT NO. 2) 

    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 NO. 2) 

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