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Home >> Lexus >> 2025 >> NX 350h >> Repair and Diagnosis >> Electrical >> Gauges >> Meter / Gauge System - Diagnostic Codes (2 Of 2), Symptom Tests & Circuit Tests >> Meter / Gauge System >> Speed Signal Circuit [11/2021 - 03/2024] >> Procedure

Speed Signal Circuit [11/2021 - 03/2024]: Procedure

  1. INSPECT COMBINATION METER ASSEMBLY (INPUT WAVEFORM) 
    GTY1068007Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Component with harness connected
    (Combination Meter Assembly)
    *b Input Waveform
    1. Check the signal waveform according to the condition(s) in the table below.
      Item Condition
      Tester connection D21-25 (SI) - Body ground
      Tool setting 5 V/DIV., 20 ms./DIV.
      Condition Ignition switch ON, wheel being rotated
      NOTE:

      Perform the inspection from the back of the connector with the connector connected.

      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

      Result  Proceed to
      The measured waveform is similar to that in the illustration A
      The measured waveform is not similar to that in the illustration
      (Stuck low)      		 B
      The measured waveform is not similar to that in the illustration
      (Stuck high)      		 C

    Result: 

    B 

    See step  6

    Result: 

    C 

    See step  9

    Result: 

    A 

    See step  2

  2. INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM) 
    GTY1068297Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Component with harness connected
    (Combination Meter Assembly)
    *b Output Waveform
    1. Check the signal waveform according to the condition(s) in the table below.
      Item Condition
      Tester connection D21-8 (+S) - Body ground
      Tool setting 5 V/DIV., 20 ms./DIV.
      Condition Ignition switch ON, wheel being rotated
      NOTE:

      Perform the inspection from the back of the connector with the connector connected.

      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.
      • The waveform (B) changes depending on the connected ECUs.

      Result

      Result  Proceed to
      The measured waveform is similar to that in the illustration A
      The measured waveform is not similar to that in the illustration
      (Stuck low)      		 B
      The measured waveform is not similar to that in the illustration
      (Stuck high)      		 C

    Result: 

    B 

    See step  4

    Result: 

    C 

    REPLACE COMBINATION METER ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    A 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (EACH ECU - COMBINATION METER ASSEMBLY) 
    1. Disconnect the A20*1 or A19*2 ECM connector.
    2. Disconnect the D1 radio and display receiver assembly connector.
    3. Disconnect the D35*3 or D37*4 stereo component amplifier assembly connector.
    4. Disconnect the D21 combination meter assembly connector.
    5. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A20-42 (SPD) - D21-8 (+S)*1 Always Below 1 Ω
      A19-24 (SPD) - D21-8 (+S)*2 Always Below 1 Ω
      D1-8 (SPD) - D21-8 (+S) Always Below 1 Ω
      D35-17 (SPD) - D21-8 (+S)*3 Always Below 1 Ω
      D37-11 (SPD) - D21-8 (+S)*4 Always Below 1 Ω
      1. *1: for Gasoline Model (for A25A-FKS)
      2. *2: for Gasoline Model (for T24A-FTS)
      3. *3: for 17 Speakers
      4. *4: for 10 Speakers

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    CHECK THE VOLTAGE AT TERMINAL SPD OF EACH ECU 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  4. INSPECT EACH ECU (INTERNAL SHORT) 
    1. Disconnect one of the connectors below.
      NOTE:

      After disconnecting a connector, perform all steps with all other devices connected.

      Connector ECU
      A20*1 ECM
      A19*2
      D1 Radio and display receiver assembly
      D35*3 Stereo component amplifier assembly
      D37*4
      1. *1: for Gasoline Model (for A25A-FKS)
      2. *2: for Gasoline Model (for T24A-FTS)
      3. *3: for 17 Speakers
      4. *4: for 10 Speakers
    2. Measure the voltage according to the value(s) in the table below.
      GTY1067979Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Combination Meter Assembly)
      NOTE:
      • Make sure to perform this inspection with the wheels stopped.
      • Perform the inspection from the back of the connector with the connector connected.

      Standard Voltage

      Tester Connection Condition Specified Condition
      D21-8 (+S) - Body ground Ignition switch ON 4.5 to 14 V
    3. Repeat steps (a) and (b) for each connected ECU.

      HINT: 

      If the waveform changes to the waveform shown in the illustration after disconnecting a connector, an internal short in the disconnected ECU is suspected.

      Result

      Result  Proceed to
      After performing the inspection procedure for all connectors, the voltage did not change to the specified voltage A
      When disconnecting the connector of the ECM, the voltage changed to the specified voltage
      (for Gasoline Model)      		 B
      When disconnecting the connector of the radio and display receiver assembly, the voltage changed to the specified voltage C
      When disconnecting the connector of the stereo component amplifier assembly, the voltage changed to the specified voltage D

    Result: 

    B 

    REPLACE ECM 

    for T24A-FTS: Refer to REMOVAL [11/2021 - ]

    for A25A-FKS: Refer to REMOVAL [11/2021 - ]

    Result: 

    C 

    REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    D 

    REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    A 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (EACH ECU - COMBINATION METER ASSEMBLY) 
    1. Disconnect the A20*1 or A19*2 ECM connector.
    2. Disconnect the D1 radio and display receiver assembly connector.
    3. Disconnect the D35*3 or D37*4 stereo component amplifier assembly connector.
    4. Disconnect the D21 combination meter assembly connector.
    5. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A20-42 (SPD)*1, A19-24 (SPD)*2, D1-8 (SPD), D35-17 (SPD)*3 or D37-11 (SPD)*4 - D21-8 (+S) Always Below 1 Ω
      A20-42 (SPD)*1, A19-24 (SPD)*2, D1-8 (SPD), D35-17 (SPD)*3, D37-11 (SPD)*4 or D21-8 (+S) - Body ground Always 10 kΩ or higher
      1. *1: for Gasoline Model (for A25A-FKS)
      2. *2: for Gasoline Model (for T24A-FTS)
      3. *3: for 17 Speakers
      4. *4: for 10 Speakers

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE COMBINATION METER ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. CHECK FOR DTC (SMART ACCESS SYSTEM WITH PUSH-BUTTON START (FOR START FUNCTION)) 
    1. Check if smart access system with push-button start (for start function) DTCs are output.

      Body Electrical > Power Source Control > Trouble Codes 

      Result

      Result Proceed to
      DTCs are not output A
      DTCs are output B

    Result: 

    B 

    GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START (FOR START FUNCTION) 

    for HEV Model: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2023 - ]

    for Gasoline Model: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2023 - ]

    Result: 

    A 

    See step  7

  7. INSPECT COMBINATION METER ASSEMBLY 

    HINT: 

    This procedure is performed to check the diode inside the combination meter assembly.

    1. Remove the combination meter assembly.

      Refer to REMOVAL [11/2021 - ]

    2. Measure the internal resistance of the combination meter assembly.

      Standard Resistance

      Tester Connection Tester Connection Condition Measured Value
      D21-6 (IG+) - D21-25 (SI)
      • Positive (+) tester probe → D21-6 (IG+)
      • Negative (-) tester probe → D21-25 (SI)
      		 Always A
      D21-6 (IG+) - D21-25 (SI)
      • Positive (+) tester probe → D21-25 (SI)
      • Negative (-) tester probe → D21-6 (IG+)
      		 Always B

      OK

      There is a large difference between the measured value (A) and the measured value (B).

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE COMBINATION METER ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - COMBINATION METER ASSEMBLY) 
    1. Disconnect the D58 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the D21 combination meter assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      D58-28 (SPDO) or D21-25 (SI) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  9. CHECK FOR DTC (SMART ACCESS SYSTEM WITH PUSH-BUTTON START (FOR START FUNCTION)) 
    1. Check if smart access system with push-button start (for start function) DTCs are output.

      Body Electrical > Power Source Control > Trouble Codes 

      Result

      Result Proceed to
      DTCs are not output A
      DTCs are output B

    Result: 

    B 

    GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START (FOR START FUNCTION) 

    for HEV Model: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2023 - ]

    for Gasoline Model: Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2023 - ]

    Result: 

    A 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - COMBINATION METER ASSEMBLY) 
    1. Disconnect the D58 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the D21 combination meter assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      D58-28 (SPDO) - D21-25 (SI) Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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