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ECU Power Source Circuit [01/2019 - 09/2022]: Procedure

WARNING: This page is about a different car, the 2022 Toyota Corolla, 2021 Toyota Corolla, and 2020 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK HYBRID VEHICLE CONTROL ECU (+B1, +B2 VOLTAGE) 
    1. Turn the power switch on (IG).
    2. Measure the voltage according to the value(s) in the table below.
      GTY887767Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Hybrid Vehicle Control ECU)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      A57-11 (+B1) - Body ground Power switch on (IG) 11 to 14 V
      I3-1 (+B2) - Body ground Power switch on (IG) 11 to 14 V
    3. Turn the power 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 I2 and I3 hybrid vehicle control ECU connectors.
    2. Measure the resistance according to the value(s) in the table below.
      GTY858179Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Hybrid Vehicle Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      I3-3 (E1) - Body ground Always Below 1 Ω
      I2-12 (E01) - Body ground Always Below 1 Ω
      I2-11 (E02) - Body ground Always Below 1 Ω
      I2-34 (E12) - Body ground Always Below 1 Ω
    3. Reconnect the I2 and I3 hybrid vehicle control ECU connectors.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [01/2019 - 09/2022] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  3. CHECK HYBRID VEHICLE CONTROL ECU (MREL VOLTAGE) 
    1. Turn the power switch on (IG).
    2. Measure the voltage according to the value(s) in the table below.
      GTY887768Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Hybrid Vehicle Control ECU)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      A57-5 (MREL) - Body ground Power switch on (IG) 11 to 14 V
    3. Turn the power switch off.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [01/2019 - 04/2020]  , or refer to  REMOVAL [04/2020 - 09/2022] 

    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.
      GTY841783Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *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 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-IG) 
    1. Remove the IGCT-IG fuse from the No. 1 engine room relay block and No. 1 junction block assembly.
      GTY843019Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 IGCT-IG Fuse
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      IGCT-IG fuse Always Below 1 Ω
    3. Install the IGCT-IG fuse.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  12

    Result: 

    OK 

    See step  6

  6. INSPECT RELAY (IGCT) 
    1. Remove the IGCT relay from the No. 1 engine room relay block and No. 1 junction block assembly.
      GTY864539Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 IGCT Relay
    2. Measure the resistance according to the value(s) in the table below.
      GTY434306Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 IGCT 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 relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE RELAY (IGCT) 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - HYBRID VEHICLE CONTROL ECU) 
    1. Disconnect the A57 and I3 hybrid vehicle control ECU connectors.
    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.
      GTY858724Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly *2 PM-IGCT Fuse Holder
      *a Front view of wire harness connector
      (to Hybrid Vehicle Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A57-11 (+B1) - 2 (PM-IGCT fuse holder) Always Below 1 Ω
      I3-1 (+B2) - 2 (PM-IGCT fuse holder) Always Below 1 Ω
    4. Install the PM-IGCT fuse.
    5. Reconnect the A57 and I3 hybrid vehicle control ECU connectors.

      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-IG fuse, PM-IGCT fuse and IGCT 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.
      GTY869772Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 PM-IGCT Fuse Holder
      *3 IGCT-IG Fuse Holder
      *4 IGCT Relay Holder

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 (IGCT relay holder) - 2 (IGCT-IG fuse holder) Always Below 1 Ω
      5 (IGCT relay holder) - 1 (PM-IGCT fuse holder) Always Below 1 Ω
    3. Install the IGCT-IG fuse, PM-IGCT fuse and IGCT 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 A57 hybrid vehicle control ECU connector.
    2. Remove the IGCT 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.
      GTY865395Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly *2 IGCT Relay Holder
      *a Front view of wire harness connector
      (to Hybrid Vehicle Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A57-5 (MREL) - 1 (IGCT relay holder) Always Below 1 Ω
      A57-5 (MREL) or 1 (IGCT relay holder) - Body ground and other terminals Always 10 kΩ or higher
    4. Install the IGCT relay.
    5. Reconnect the A57 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 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.
      GTY875531Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 IGCT Relay Holder

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (IGCT relay holder) - Body ground Always Below 1 Ω
    3. Install the IGCT relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [01/2019 - 09/2022] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - HYBRID VEHICLE CONTROL ECU) 
    1. Remove the PM-IGCT fuse from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Disconnect the A57 and I3 hybrid vehicle control ECU connectors.
    3. Measure the resistance according to the value(s) in the table below.
      GTY858724Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly *2 PM-IGCT Fuse Holder
      *a Front view of wire harness connector
      (to Hybrid Vehicle Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      A57-11 (+B1) or 2 (PM-IGCT fuse holder) - Body ground and other terminals Always 10 kΩ or higher
      I3-1 (+B2) or 2 (PM-IGCT fuse holder) - Body ground and other terminals Always 10 kΩ or higher
    4. Reconnect the A57 and I3 hybrid vehicle control ECU connectors.
    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-IG fuse, PM-IGCT fuse and IGCT 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.
      GTY869772Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 PM-IGCT Fuse Holder
      *3 IGCT-IG Fuse Holder
      *4 IGCT Relay Holder
      STANDARD RESISTANCE:

      Tester Connection Condition Specified Condition
      3 (IGCT relay holder) or 2 (IGCT-IG fuse holder) - Body ground and other terminals Always 10 kΩ or higher
      5 (IGCT relay holder) or 1 (PM-IGCT fuse holder) - Body ground and other terminals Always 10 kΩ or higher
    3. Install the IGCT-IG fuse, PM-IGCT fuse and IGCT relay.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE RELAY (IGCT-IG) 

    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-IG) 

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