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ECU Power Source Circuit [10/2022 - 08/2023]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK HARNESS AND CONNECTOR (BATT TERMINAL VOLTAGE) 
    1. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      C35-2 (BATT) - Body ground Ignition switch off 11 to 14 V

      Result

      Proceed to
      OK
      NG
      GTY1128058Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Transmission Floor Shift Assembly (Shift Control ECU))

    Result: 

    NG 

    See step  8

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (IGR TERMINAL VOLTAGE) 
    1. Turn the ignition switch to ON.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      C35-3 (IGR) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG
      GTY1128057Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Transmission Floor Shift Assembly (Shift Control ECU))
    3. Turn the ignition switch off.

    Result: 

    NG 

    See step  9

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (IGP TERMINAL VOLTAGE) 
    1. Turn the ignition switch to ON.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      C35-1 (IGP) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG
      GTY1128060Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Transmission Floor Shift Assembly (Shift Control ECU))
    3. Turn the ignition switch off.

    Result: 

    NG 

    See step  10

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ECU - BODY GROUND) 
    1. Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C35-9 (E1) - Body ground Always Below 1 Ω
      C35-23 (E12) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Connect the transmission floor shift assembly (shift control ECU) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ECU - BODY GROUND) 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (MA1, BAT1 TERMINAL VOLTAGE) 
    1. Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B58-6 (MA1) - Body ground Ignition switch off 11 to 14 V
      B58-8 (BAT1) - Body ground Ignition switch off 11 to 14 V

      Result

      Proceed to
      OK
      NG
    3. Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (IGR1 TERMINAL VOLTAGE) 
    1. Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    2. Turn the ignition switch to ON.
      NOTE:

      Turning the ignition switch to ON with the connector disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B56-5 (IGR1) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG
    4. Turn the ignition switch off.
    5. Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    See step  13

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - BODY GROUND) 
    1. Disconnect the B56 and B58 shift control actuator assembly (shift actuator ECU) connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B58-7 (E01) - Body ground Always Below 1 Ω
      B56-7 (E02) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG
    3. Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [10/2022 - 08/2023] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  8. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the P CON MAIN fuse from the No. 2 engine room relay block and No. 2 junction block assembly.
    2. Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C35-2 (BATT) - 2 (P CON MAIN fuse holder) Always Below 1 Ω
      C35-2 (BATT) or 2 (P CON MAIN fuse holder) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the shift control actuator assembly (shift actuator ECU) connector.
    5. Install the P CON MAIN fuse.

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

  9. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ECU - POWER DISTRIBUTION BOX ASSEMBLY) 
    1. Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    2. Disconnect the C90 power distribution box assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C90-36 - C35-3 (IGR) Always Below 1 Ω
      C90-36 or C35-3 (IGR) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the power distribution box assembly connector.
    5. Connect the transmission floor shift assembly (shift control ECU) connector.

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - POWER DISTRIBUTION BOX ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ECU - POWER DISTRIBUTION BOX ASSEMBLY) 

  10. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the ECU-IGP NO. 3 fuse from the No. 2 engine room relay block and No. 2 junction block assembly.
    2. Disconnect the C35 transmission floor shift assembly (shift control ECU) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C35-1 (IGP) - 2 (ECU-IGP NO. 3 fuse holder) Always Below 1 Ω
      C35-1 (IGP) or 2 (ECU-IGP NO. 3 fuse holder) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the transmission floor shift assembly (shift control ECU) connector.
    5. Install the ECU-IGP NO. 3 fuse.

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT CONTROL ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

  11. CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the P CON MTR fuse from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B58-6 (MA1) - 2 (P CON MTR fuse holder) Always Below 1 Ω
      B58-6 (MA1) or 2 (P CON MTR fuse holder) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the shift control actuator assembly (shift actuator ECU) connector.
    5. Install the P CON MTR fuse.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT ACTUATOR ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY) 

    Result: 

    OK 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 
    1. Remove the P CON MAIN fuse from the No. 2 engine room relay block and No. 2 junction block assembly.
    2. Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B58-8 (BAT1) - 2 (P CON MAIN fuse holder) Always Below 1 Ω
      B58-8 (BAT1) or 2 (P CON MAIN fuse holder) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the shift control actuator assembly (shift actuator ECU) connector.
    5. Install the P CON MAIN fuse.

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT ACTUATOR ECU - NO. 2 ENGINE ROOM RELAY BLOCK AND NO. 2 JUNCTION BLOCK ASSEMBLY) 

  13. CHECK HARNESS AND CONNECTOR (SHIFT ACTUATOR ECU - POWER DISTRIBUTION BOX ASSEMBLY) 
    1. Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    2. Disconnect the A72 power distribution box assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A72-13 - B56-5 (IGR1) Always Below 1 Ω
      A72-13 or B56-5 (IGR1) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG
    4. Connect the power distribution box assembly connector.
    5. Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - POWER DISTRIBUTION BOX ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SHIFT ACTUATOR ECU - POWER DISTRIBUTION BOX ASSEMBLY) 

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