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Home >> Lexus >> 2021 >> LC 500h >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Meter / Gauge System - Diagnostic Codes, Symptom & Circuit Tests >> Meter / Gauge System >> Speed Signal Circuit [01/2017 - 06/2019] >> Procedure

Speed Signal Circuit [01/2017 - 06/2019]: Procedure

  1. INSPECT 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 Power 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. INSPECT 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 Power switch on (IG) 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  4

    Result: 

    OK 

    See step  3

  3. INSPECT 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 power 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 Power 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 [01/2017 - ] 

    Result: 

    NG 

    REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [01/2017 - 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 [01/2017 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  5. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - EACH ECU) 
    1. Disconnect the P66 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the X49 stereo component amplifier assembly connector.
    3. Disconnect the X51 vehicle approaching speaker assembly connector.
    4. Disconnect the P47 navigation ECU connector.
    5. Disconnect the P43 radio receiver assembly connector.
    6. Disconnect the Z2 map light sub-assembly connector.
    7. 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. INSPECT VEHICLE APPROACHING SPEAKER ASSEMBLY (SHORT CIRCUIT IN VEHICLE APPROACHING SPEAKER ASSEMBLY) 
    1. Reconnect the P66 certification ECU (smart key ECU assembly) connector.
    2. Reconnect the X49 stereo component amplifier assembly connector.
    3. Reconnect the P47 navigation ECU connector.
    4. Reconnect the Z2 map light sub-assembly connector.
    5. Reconnect the P43 radio receiver assembly connector.
    6. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Power 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 VEHICLE APPROACHING SPEAKER ASSEMBLY 

    Result: 

    B 

    See step  7

  7. INSPECT RADIO RECEIVER ASSEMBLY (SHORT CIRCUIT IN RADIO RECEIVER) 
    1. Disconnect the P43 radio receiver assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Power 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 

    Result: 

    NG 

    See step  8

  8. INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (SHORT CIRCUIT IN STEREO COMPONENT AMPLIFIER) 
    1. Disconnect the X49 stereo component amplifier assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Power 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 

    Result: 

    NG 

    See step  9

  9. INSPECT NAVIGATION ECU (SHORT CIRCUIT IN NAVIGATION ECU) 
    1. Disconnect the P47 navigation ECU connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Power 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 

    Result: 

    NG 

    See step  10

  10. INSPECT MAP LIGHT SUB-ASSEMBLY (SHORT CIRCUIT IN NAVIGATION ECU) 
    1. Disconnect the Z2 map light sub-assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P25-19 (+S) - Other terminals and body ground Power 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 

    Result: 

    NG 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 

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