LEMON Manuals: Even more car manuals for everyone
Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 138 (Hybrid Control System - Diagnostic Codes (6 Of 7)) >> HYBRID CONTROL SYSTEM (for PHEV Model) >> DTC P3123-87: Lost Communication with Drive Motor Control Module "A" from Hybrid/EV Control Module Missing Message [08/2023 - ] >> Procedure

DTC P3123-87: Lost Communication with Drive Motor Control Module "A" from Hybrid/EV Control Module Missing Message [08/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 450h+ and 2024 Lexus RX 450h+. However, it is still accessible from the selected car via links, so may be relevant.
  1. CLEAR DTC 

    Refer to PROCEDURE - Step 3

    Result

    Proceed to
    NEXT

    Result: 

    NEXT 

    See step  2

  2. CHECK DIAGNOSIS RELATED INFORMATION (HYBRID CONTROL) 

    Pre-procedure1

    • Turn the ignition switch to ON and wait for 2 minutes or more.
    • Enter the following menus: Powertrain / Hybrid Control / Utility / Diagnosis Related Information.

      Powertrain > Hybrid Control > Utility 

      Tester Display
      Diagnosis Related Information

      Result

      Result  Proceed to
      P3123-87 is listed in Diagnosis Related Information. A
      P3123-87 is not listed in Diagnosis Information. B

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    B 

    CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [08/2023 - ] 

    Result: 

    A 

    See step  3

  3. CHECK DTC OUTPUT (HYBRID CONTROL) 

    Pre-procedure1

    • None.
    • Check for DTCs.

      Powertrain > Hybrid Control > Trouble Codes 

      Result

      Result  Proceed to
      P3123-87 is output A
      P3123-87 is not output B

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    B 

    CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [08/2023 - ] 

    Result: 

    A 

    See step  4

  4. CHECK CONNECTOR CONNECTION CONDITION (HYBRID VEHICLE CONTROL ECU CONNECTOR) 

    Refer to PROCEDURE - Step 1

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    CONNECT SECURELY 

    Result: 

    OK 

    See step  5

  5. CHECK CONNECTOR CONNECTION CONDITION (HYBRID MOTOR CONTROL INVERTER ASSEMBLY CONNECTOR) 

    HINT: 

    Refer to PROCEDURE - Step 3

    Result

    Result Proceed to
    OK A
    NG (The connector is not connected securely.) B
    NG (The terminals are not making secure contact or are deformed, or water or foreign matter exists in the connector.) C

    Result: 

    B 

    CONNECT SECURELY 

    Result: 

    C 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    A 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (HYBRID MOTOR CONTROL INVERTER ASSEMBLY POWER SOURCE CIRCUIT) 
    WARNING:

    Be sure to wear insulated gloves.

    Pre-procedure1

    • Check that the service plug grip is not installed.
      NOTE:

      After removing the service plug grip, do not turn the ignition switch to ON (READY), unless instructed by the appropriate service information because this may cause a malfunction.

    • Disconnect the hybrid motor control inverter assembly connector.
      GTY1203769Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • Measure the resistance according to the value(s) in the table below.
      GTY1204801Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Hybrid Motor Control Inverter Assembly)

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A41-9 (GND1) - Body ground Ignition switch off Below 1 Ω Ω
      A41-8 (GND2) - Body ground Ignition switch off Below 1 Ω Ω
    • Connect the cable to the negative (-) auxiliary battery terminal.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      A41-36 (+B) - Body ground Ignition switch ON 11 to 14 V V
      A41-35 (+B2) - Body ground Ignition switch ON 11 to 14 V V
      NOTE:

      Turning the ignition switch to ON with the hybrid motor control inverter assembly disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Turn the ignition switch off.
    • Disconnect the cable from the negative (-) auxiliary battery terminal.
    • Reconnect the hybrid motor control inverter assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (HYBRID MOTOR CONTROL INVERTER ASSEMBLY - HYBRID VEHICLE CONTROL ECU) 
    WARNING:

    Be sure to wear insulated gloves.

    Pre-procedure1

    • Check that the service plug grip is not installed.
      NOTE:

      After removing the service plug grip, do not turn the ignition switch to ON (READY), unless instructed by the appropriate service information because this may cause a malfunction.

    • Disconnect the hybrid motor control inverter assembly connector.
      GTY1203769Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • Disconnect the hybrid vehicle control ECU connector.
    • Connect the cable to the negative (-) auxiliary battery terminal.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.
      GTY1205622Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Hybrid Motor Control Inverter Assembly)
      *b Front view of wire harness connector
      (to Hybrid Vehicle Control ECU)

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      A21-2 (HMCH) - Body ground Ignition switch ON Below 1 V V
      A21-1 (HMCL) - Body ground Ignition switch ON Below 1 V V
      NOTE:

      Turning the ignition switch to ON with the hybrid vehicle control ECU connector and the hybrid motor control inverter assembly disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

    • Turn the ignition switch off.
    • Disconnect the cable from the negative (-) auxiliary battery terminal.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)

      Tester Connection Condition Specified Condition Result
      A41-4 (HMCL) - A21-1 (HMCL) Ignition switch off Below 1 Ω Ω
      A41-3 (HMCH) - A21-2 (HMCH) Ignition switch off Below 1 Ω Ω

      Standard Resistance (Check for Short)

      Tester Connection Condition Specified Condition Result
      A41-4 (HMCL) or A21-1 (HMCL) - Body ground and other terminals Ignition switch off 10 kΩ or higher kΩ
      A41-3 (HMCH) or A21-2 (HMCH) - Body ground and other terminals Ignition switch off 10 kΩ or higher kΩ

      HINT: 

      As there might be an intermittent malfunction, inspect the following items even if the measured resistance is as specified.

      Check that each connector between the hybrid motor control inverter assembly and hybrid vehicle control ECU is not loose or disconnected.

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Reconnect the hybrid vehicle control ECU connector.
    • Reconnect the hybrid motor control inverter assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HYBRID VEHICLE CONTROL ECU ASSEMBLY 
    WARNING:

    Be sure to wear insulated gloves.

    Pre-procedure1

    • Check that the service plug grip is not installed.
      NOTE:

      After removing the service plug grip, do not turn the ignition switch to ON (READY), unless instructed by the appropriate service information because this may cause a malfunction.

    • Disconnect the hybrid motor control inverter assembly connector.
      GTY1203769Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • Measure the resistance according to the value(s) in the table below.
      GTY1204473Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Hybrid Vehicle Control ECU)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A21-1 (HMCL) - A21-2 (HMCH) Ignition switch off 110 to 130 Ω Ω

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Reconnect the hybrid motor control inverter assembly connector.

    Result: 

    OK 

    REPLACE HYBRID MOTOR CONTROL INVERTER ASSEMBLY. Refer to  REMOVAL [08/2023 - ] 

    Result: 

    NG 

    REPLACE HYBRID VEHICLE CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

scientia non olet · About LEMON Manuals