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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 12 (Electronic A/T Shift Lever System - Diagnostic Codes (2 Of 2) & Circuit Tests) >> Electronic Shift Lever System >> DTC P177C-62: Gear Lever Position / Transmission Position Signal Compare Failure [08/2023 - ] >> Procedure

DTC P177C-62: Gear Lever Position / Transmission Position Signal Compare Failure [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 VEHICLE CONDITION 
    1. Check for removal and installation history of the shift control actuator assembly (shift actuator ECU).

      HINT: 

      If the shift control actuator assembly (shift actuator ECU) has been replaced or removed, make sure to perform actuator position learning. Check for removal and installation history as this DTC may be stored if the learning has not been completed.

      Result

      Result Proceed to
      History exists A
      No history B

    Result: 

    B 

    See step  5

    Result: 

    A 

    See step  2

  2. CLEAR DTC 

    Pre-procedure1

    • Turn the ignition switch to ON.
    • Clear the DTCs.

      Powertrain > Transmission > Clear DTCs 

      Result

      Proceed to
      NEXT

    Post-procedure1

    • Turn the ignition switch off.
    • Disconnect the GTS.
    • Leave the vehicle as is for 60 seconds or more.
      NOTE:
      • Do not connect the GTS.
      • Do not depress the brake pedal.
      • Do not open/close any of the doors.

    Result: 

    NEXT 

    See step  3

  3. PERFORM UTILITY (ACT POSITION LEARNING) 

    Pre-procedure1

    • Turn the ignition switch to ON.
    • Perform ACT Position Learning.

      HINT: 

      Refer to UTILITY [10/2022 - ]

      Powertrain > Transmission > Utility 

      Tester Display
      ACT Position Learning

      Result

      Proceed to
      NEXT

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    NEXT 

    See step  4

  4. CHECK DTC OUTPUT 

    Pre-procedure1

    • Start the engine.
    • With the brake pedal depressed, perform a shift operation then change the shift state to D.

      Check that D is illuminated on the shift position indicator.

    • With the brake pedal depressed, perform a shift operation then change the shift state to R.

      Check that R is illuminated on the shift position indicator.

    • Press the P position switch to change the shift state to P.
    • Check for DTCs.

      Powertrain > Transmission > Trouble Codes 

      Result

      Result Proceed to
      P177C-62 is not output A
      P177C-62 is output B

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    A 

    END 

    Result: 

    B 

    See step  5

  5. CHECK DTC OUTPUT (TRANSMISSION) 

    Pre-procedure1

    • Turn the ignition switch to ON.
    • Check if DTCs are output.

      Powertrain > Transmission > Trouble Codes 

      Result

      Result Proceed to
      No DTCs in the table below are output A
      P177C-62 and any DTCs in the table below are output B
      Priority Relevant DTC
      1 P1790-14 Gear Shift Actuator "A" Supply Voltage "A" Circuit Short to Ground or Open
      P1796-14 Gear Shift Actuator "B" Supply Voltage "A" Circuit Short to Ground or Open
      U1176-87 Lost Communication with Gear Shift Control Module "A" (ch2) Missing Message
      U0291-00 Lost Communication with Gear Shift Control Module "B" (System 2) Missing Message
      P1789-00 Lost Communication with Gear Shift Control Module "A" from "B" (Sub CPU) Missing Message
      P1753-87 Lost Communication with Gear Shift Control Module "B" (Local-CAN) Missing Message
      U1170-00 Lost Communication with Brake System Control Module (Gear Shift Control Module "A")
      P179C-49 Gear Shift Actuator "A" Control Circuit Internal Electronic Failure
      P179D-49 Gear Shift Actuator "B" Control Circuit Internal Electronic Failure
      P18B2-00 Gear Shift Control Module "B" Motor Angle Sensor "A" Performance
      P18B6-00 Gear Shift Control Module "B" Motor Angle Sensor "B" Performance
      P18B5-62 Gear Shift Actuator "A" Phase U-V-W Current Sensor Signal Compare Failure
      P18B9-62 Gear Shift Actuator "B" Phase U-V-W Current Sensor Signal Compare Failure
      P0914-2B Gear Shift Position Circuit "A" Range/Performance Signal Cross Coupled
      P091A-2B Gear Shift Position Circuit "B" Range/Performance Signal Cross Coupled
      P1779-49 Gear Shift Control Module Backup Power Supply Internal Electronic Failure
      P1779-96 Gear Shift Control Module Backup Power Supply Component Internal Failure
      P177A-87 Lost Communication with Gear Shift Control Module Backup Power Supply Missing Message
      2 P179E-00 Gear Shift Actuator "A" Performance
      P179F-00 Gear Shift Actuator "B" Performance

      HINT: 

      Items in the above table are listed in order of priority.

    Post-procedure1

    • Turn the ignition switch off.

    Result: 

    B 

    GO TO DTC CHART 

    for Automatic Transaxle System: Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2023 - 10/2024] , or refer to DIAGNOSTIC TROUBLE CODE CHART [10/2024 - ]

    for Electronic Shift Lever System: Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2023 - ]

    Result: 

    A 

    See step  6

  6. INSPECT BATTERY TERMINAL (CONTACT PROBLEM) 
    1. Check the connection of the battery terminal.

      OK

      The battery is connected securely and there are no contact problems.

      HINT: 

      Perform an inspection with consideration of a power supply voltage interruption due to a loose terminal, poor connection, etc.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    CONNECT SECURELY 

    Result: 

    OK 

    See step  7

  7. CHECK VEHICLE CONDITION 
    1. Choose the model to be inspected.

      Result

      Result Proceed to
      w/o Advanced Park (Remote Controlled) A
      w/ Advanced Park (Remote Controlled) B

    Result: 

    B 

    See step  13

    Result: 

    A 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B56-8 (BUB1) - Body ground Ignition switch ON 8 to 14 V V
      B56-6 (MA2) - Body ground Ignition switch ON 11 to 14 V V

      Result

      Proceed to
      OK
      NG
      NOTE:

      As other DTCs will be stored when the ignition switch is turned to ON with the connector disconnected, be sure to clear the DTCs after the inspection.

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (BATTERY - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B58-8 (BAT1) - Body ground Always 11 to 14 V V
      B58-6 (MA1) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Result: 

    OK 

    See step  10

  10. INSPECT AUTOMATIC TRANSAXLE ASSEMBLY (STUCK/FREE SPINNING OFF PARKING LOCK SHAFT) 
    1. Check that the parking lock shaft.

      Refer to ON-VEHICLE INSPECTION [10/2022 - ]

      OK

      The parking lock shaft is not stuck, and moves reasonably smoothly to each shift position.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    REPLACE AUTOMATIC TRANSAXLE ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

  11. CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    • Disconnect the H116 integration control supply (integrated capacitor) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      B56-8 (BUB1) - H116-9 (BUAE) Always Below 1 Ω Ω
      B56-6 (MA2) - H116-19 (BUA) Always Below 1 Ω Ω
      B56-8 (BUB1) or H116-9 (BUAE) - Body ground and other terminals Always 10 kΩ or higher kΩ
      B56-6 (MA2) or H116-19 (BUA) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the integration control supply (integrated capacitor) connector.
    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Result: 

    OK 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) - BODY GROUND) 

    Pre-procedure1

    • Disconnect the B56 and B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

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

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  13. CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B56-8 (BUB1) - Body ground Ignition switch ON 8 to 14 V V
      B56-6 (MA2) - Body ground Ignition switch ON 11 to 14 V V

      Result

      Proceed to
      OK
      NG
      NOTE:

      As other DTCs will be stored when the ignition switch is turned to ON with the connector disconnected, be sure to clear the DTCs after the inspection.

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    See step  17

    Result: 

    OK 

    See step  14

  14. CHECK HARNESS AND CONNECTOR (BATTERY - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B58-8 (BAT1) - Body ground Always 11 to 14 V V
      B58-6 (MA1) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    See step  10

    Result: 

    NG 

    See step  15

  15. CHECK HARNESS AND CONNECTOR (BATTERY - SECOND POWER SUPPLY REMOTE PARKING CIRCUIT) 

    Pre-procedure1

    • Disconnect the H194 and H195 second power supply remote parking circuit connector.
    • Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      H194-1 (B1E1) - Body ground Always 11 to 14 V V
      H195-2 (B1A1) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the second power supply remote parking circuit connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - SECOND POWER SUPPLY REMOTE PARKING CIRCUIT) 

    Result: 

    OK 

    See step  16

  16. CHECK HARNESS AND CONNECTOR (SECOND POWER SUPPLY REMOTE PARKING CIRCUIT - SHIFT ACTUATOR ECU AND GND TERMINAL) 

    Pre-procedure1

    • Disconnect the H194 and H196 second power supply remote parking circuit connector.
    • Disconnect the B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      H194-8 (BOE) - B58-8 (BAT1) Always Below 1 Ω Ω
      H196-2 (BOA) - B58-6 (MA1) Always Below 1 Ω Ω
      H194-8 (BOE) or B58-8 (BAT1) - Body ground and other terminals Always 10 kΩ or higher kΩ
      H196-2 (BOA) or B58-6 (MA1) - Body ground and other terminals Always 10 kΩ or higher kΩ
      H194-10 (GND) - Body ground Always Below 1 Ω Ω

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the second power supply remote parking circuit connector.
    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    REPLACE SECOND POWER SUPPLY REMOTE PARKING CIRCUIT. Refer to  REMOVAL [08/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  17. CHECK HARNESS AND CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Pre-procedure1

    • Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
    • Disconnect the H191 integration control supply (integrated capacitor) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      B56-8 (BUB1) - H191-9 (BUAE) Always Below 1 Ω Ω
      B56-6 (MA2) - H191-19 (BUA) Always Below 1 Ω Ω
      B56-8 (BUB1) or H191-9 (BUAE) - Body ground and other terminals Always 10 kΩ or higher kΩ
      B56-6 (MA2) or H191-19 (BUA) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the integration control supply (integrated capacitor) connector.
    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (INTEGRATION CONTROL SUPPLY (INTEGRATED CAPACITOR) - SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU)) 

    Result: 

    OK 

    See step  18

  18. CHECK HARNESS AND CONNECTOR (SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU) - BODY GROUND) 

    Pre-procedure1

    • Disconnect the B56 and B58 shift control actuator assembly (shift actuator ECU) connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

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

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the shift control actuator assembly (shift actuator ECU) connector.

    Result: 

    OK 

    REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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