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DTC P0A1B-1F: Generator Control Module Circuit Intermittent [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. CHECK DTC OUTPUT 

    Pre-procedure1

    1. None.

      Procedure1

    2. Check for DTCs.

      Powertrain > Hybrid Control > Trouble Codes 

      Powertrain > Motor Generator > Trouble Codes 

      Result

      Result Proceed to
      P0A1B-1F only is output. A
      DTCs of hybrid control system in the tables below are output. B
      DTCs of motor generator control system in the tables below are output. C
      Malfunction Content System Relevant DTC
      Communication malfunction Motor generator control system P3124-87 Lost Communication between Drive Motor "A" and HV ECU Missing Message
      Hybrid control system P3123-87 Lost Communication with Drive Motor Control Module "A" from Hybrid/EV Control Module Missing Message
      U0110-87 Lost Communication with Drive Motor Control Module "A" Missing Message

      Post-procedure1

    3. Turn the ignition switch off.

    Result: 

    B 

    GO TO DTC CHART (HYBRID CONTROL SYSTEM). Refer to  DIAGNOSTIC TROUBLE CODE CHART [08/2023 - 10/2024]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2024 - ] 

    Result: 

    C 

    GO TO DTC CHART (MOTOR GENERATOR CONTROL SYSTEM)  . Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2023 - ] .

    Result: 

    A 

    See step  2

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

    See 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  3

  3. CHECK AUXILIARY BATTERY TERMINAL (CONTACT PROBLEM) 
    1. Check the connection of the auxiliary battery terminal.

      OK

      The terminal is connected securely and there is no contact problem.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    CONNECT SECURELY 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (HYBRID MOTOR CONTROL INVERTER ASSEMBLY- IGCT-RELAY) 
    WARNING:

    Be sure to wear insulated gloves.

    Pre-procedure1

    1. 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 service information because this may cause a malfunction.

    2. Disconnect the hybrid motor control inverter assembly connector.
    3. Remove the IGCT-IG relay from the No. 1 engine room relay block and No. 1 junction block assembly.

      Procedure1

    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A41-36 (+B) - 5 (IGCT-IG relay) Ignition switch off Below 1 Ω
      A41-35 (+B2) - 5 (IGCT-IG relay) Ignition switch off Below 1 Ω
      A41-9 (GND1) - Body ground Ignition switch off Below 1 Ω
      A41-8 (GND2) - Body ground Ignition switch off Below 1 Ω

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    5. Install the IGCT-IG relay.
    6. Reconnect the hybrid motor control inverter assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK FOR INTERMITTENT PROBLEMS 
    1. Check for intermittent problems.

      HINT: 

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

      1. Check the connection and terminal contact pressure of the connectors and wire harnesses between the auxiliary battery and the hybrid motor control inverter assembly.

        Result

        There are no abnormalities in the wire harnesses and connectors.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REFER TO REPLACE HYBRID MOTOR CONTROL INVERTER ASSEMBLY PARTS. Refer to  DTC CHECK / CLEAR [08/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA 

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