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Home >> Lexus >> 2021 >> LC 500 2D Convertible >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Meter / Gauge System - Diagnostic Codes, Symptom Tests & Circuit Tests (Convertible) >> Meter / Gauge System >> Speed Signal Circuit [07/2020 - 05/2023] >> Procedure

Speed Signal Circuit [07/2020 - 05/2023]: Procedure

  1. CHECK ECU TERMINAL VOLTAGE (INPUT VOLTAGE) 
    1. Disconnect the combination meter assembly connector.
      GTY827461Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If any of the ECUs specified in the wiring diagram supplies power to the combination meter assembly, the combination meter assembly will output a waveform.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  5

    Result: 

    OK 

    See step  2

  2. CHECK COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE) 
    1. Reconnect the P25 combination meter assembly connector.
    2. Disconnect the skid control ECU assembly connector.
      GTY787716Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU Assembly)
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      A9-22 (SP1) - Body ground Engine switch on (IG) 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  4

    Result: 

    OK 

    See step  3

  3. CHECK COMBINATION METER ASSEMBLY (INPUT WAVEFORM) 
    1. Check the input waveform.
      GTY783479Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Combination Meter Assembly)
      1. Reconnect the A9 skid control ECU assembly connector.
      2. Remove the combination meter assembly with the connector(s) still connected.
      3. Connect an oscilloscope to terminal P25-20 (SI) and body ground.
      4. Turn the engine switch on (IG).
      5. Turn a wheel slowly.
      6. Check the signal waveform according to the condition(s) in the table below.
        Item Condition
        Tool setting 5 V/DIV., 20 ms./DIV.
        Vehicle condition Engine switch on (IG) wheel being rotated

        OK

        The waveform is similar to that shown in the illustration.

        HINT: 

        When the system is functioning normally, one wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE COMBINATION METER ASSEMBLY. Refer to  REMOVAL [07/2020 - ] 

    Result: 

    NG 

    REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [07/2020 - 05/2023] 

  4. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - SKID CONTROL ECU ASSEMBLY) 
    1. Disconnect the P25 combination meter assembly connector.
    2. Disconnect the A9 skid control ECU assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      P25-20 (SI) - A9-22 (SP1) Always Below 1 Ω
      P25-20 (SI) - Other terminals and body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE COMBINATION METER ASSEMBLY. Refer to  REMOVAL [07/2020 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  5. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - EACH ECU) 
    1. Disconnect the P25 combination meter assembly connector.
    2. Disconnect the P66 certification ECU (smart key ECU assembly) connector.
    3. Disconnect the X49 stereo component amplifier assembly connector.
    4. Disconnect the A58 ECM connector.
    5. Disconnect the P47 navigation ECU connector.
    6. Disconnect the P43 radio receiver assembly connector.
    7. Disconnect the Z4 map light sub-assembly connector.
    8. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. CHECK ECM (SHORT CIRCUIT IN ECM) 
    1. Disconnect the combination meter assembly connector.
      GTY958896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Disconnect the A58 ECM connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If the result is as specified, there may be a short circuit in the vehicle approaching speaker assembly.

      Result

      Result Proceed to
      OK A
      NG B

    Result: 

    A 

    REPLACE ECM. Refer to  REMOVAL [07/2020 - 05/2023] 

    Result: 

    B 

    See step  7

  7. CHECK RADIO RECEIVER ASSEMBLY (SHORT CIRCUIT IN RADIO RECEIVER) 
    1. Disconnect the combination meter assembly connector.
      GTY958896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Disconnect the P43 radio receiver assembly connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If the result is as specified, there may be a short circuit in the radio receiver assembly.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE RADIO RECEIVER ASSEMBLY. Refer to  REMOVAL [07/2020 - 05/2023] 

    Result: 

    NG 

    See step  8

  8. CHECK STEREO COMPONENT AMPLIFIER ASSEMBLY (SHORT CIRCUIT IN STEREO COMPONENT AMPLIFIER) 
    1. Disconnect the combination meter assembly connector.
      GTY958896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Disconnect the X49 stereo component amplifier assembly connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If the result is as specified, there may be a short circuit in the stereo component amplifier assembly.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY. Refer to  REMOVAL [07/2020 - 05/2023] 

    Result: 

    NG 

    See step  9

  9. CHECK NAVIGATION ECU (SHORT CIRCUIT IN NAVIGATION ECU) 
    1. Disconnect the combination meter assembly connector.
      GTY958896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Disconnect the P47 navigation ECU connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If the result is as specified, there may be a short circuit in the navigation ECU.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE NAVIGATION ECU. Refer to  REMOVAL [07/2020 - 05/2023] 

    Result: 

    NG 

    See step  10

  10. CHECK MAP LIGHT SUB-ASSEMBLY (SHORT CIRCUIT IN MAP LIGHT SUB-ASSEMBLY) 
    1. Disconnect the combination meter assembly connector.
      GTY958896Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Combination Meter Assembly)
    2. Disconnect the Z4 map light sub-assembly connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V

      HINT: 

      If the result is as specified, there may be a short circuit in the map light sub-assembly.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MAP LIGHT SUB-ASSEMBLY. Refer to  REMOVAL [07/2020 - 05/2023] 

    Result: 

    NG 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 

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