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METER / GAUGE SYSTEM Speed Signal Circuit

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DTC Code DTC Name
  Speed Signal Circuit
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DESCRIPTION

The combination meter assembly receives the vehicle speed signal from this circuit. The wheel speed sensors produce an output that varies according to the vehicle speed. The wheel speed sensor output is received by the brake actuator assembly (skid control ECU) which uses this information to create the vehicle speed signal*a. The vehicle speed signal consists of pulses sent to the combination meter assembly from the brake actuator assembly (skid control ECU). To create this signal, 12 V is output from IG2 which is behind a resistor in the combination meter assembly. This voltage is sent to the brake actuator assembly (skid control ECU). The pulse signal is created by switching the transistor in the brake actuator assembly (skid control ECU) on and off, making the voltage on the wire drop to 0 V. A similar system is used for the output of this signal from the combination meter assembly via terminal +S. A voltage of 12 V or 5 V is applied to terminal +S from each ECU or relay that is connected to this terminal. The transistor in the combination meter assembly is controlled by the signal from the brake actuator assembly (skid control ECU). When this transistor is turned on, this transistor makes the voltage supplied by the various ECUs (via their respective internal resistors) drop to 0 V. Each ECU connected to terminal +S of the combination meter assembly controls its respective system based on this pulse signal.


Tip:

This circuit is used for the systems connected to terminal +S. This signal is not used for combination meter assembly operation. Combination meter assembly components such as the speedometer operate using data received via CAN communication.

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WIRING DIAGRAM

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CAUTION / NOTICE / HINT

Note:

Before replacing the ECM, certification ECU (smart key ECU assembly) or DCM (telematics transceiver)*, refer to Service Bulletin.


  • *: for Lexus Enform Remote Compatible Type

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PROCEDURE


  1. Click here

    INSPECT ECU TERMINAL VOLTAGE (INPUT VOLTAGE)


    1. B0066YIC22
      *a

      Front view of wire harness connector

      (to Combination Meter Assembly)

      Disconnect the O3 combination meter assembly connector.

    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

      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

  2. Click here

    INSPECT COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE)


    1. Reconnect the O3 combination meter assembly connector.

    2. B0066KWC92
      *a

      Front view of wire harness connector

      (to Brake Actuator Assembly (Skid Control ECU))

      Disconnect the A15 brake actuator assembly (skid control ECU) connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A15-11 (SP1) - Body ground Engine switch on (IG) 11 to 14 V
      Result
      Proceed to
      OK
      NG

  3. Click here

    INSPECT BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU) (INPUT WAVEFORM)


    1. B0066TXC21
      *a

      Component with harness connected

      (Combination Meter Assembly)

      Check the input waveform.


      1. Reconnect the A15 brake actuator assembly (skid control ECU) connector.

      2. Remove the combination meter assembly with the connector(s) still connected.

      3. Connect an oscilloscope to terminal O3-20 (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.
        Tip:

        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

    • OK

      REPLACE COMBINATION METER ASSEMBLYClick here

    • NG

      REPLACE BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU) for LHD:Click here

      REPLACE BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU) for RHD:Click here

  4. Click here

    CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU))


    1. Disconnect the O3 combination meter assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      O3-20 (SI) - A15-11 (SP1) Always Below 1 Ω
      O3-20 (SI) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE COMBINATION METER ASSEMBLYClick here

    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

  5. Click here

    CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - EACH ECU)


    1. Disconnect the A78 ECM connector.

    2. Disconnect the O6 certification ECU (smart key ECU assembly) connector.

    3. Disconnect the O65 DCM (Telematics Transceiver) connector*1.

    4. Disconnect the O57 radio receiver assembly connector*2, *3.

    5. Disconnect the O70 radio receiver assembly connector*4.

    6. Disconnect the T20*2, *3 or P21*5 stereo component amplifier assembly connector.


      • *1: w/ Telematics Transceiver

      • *2: w/ Navigation System

      • *3: w/ Audio and Visual System with Parking Assist Monitor System

      • *4: w/ Audio and Visual System without Parking Assist Monitor System

      • *5: w/ Audio and Visual System without Parking Assist Monitor System (for 10 Speakers)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

  6. Click here

    INSPECT ECM (SHORT CIRCUIT IN ECM)


    1. Reconnect the O6 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the O65 DCM (Telematics Transceiver) connector*1.

    3. Reconnect the O57 radio receiver assembly connector*2, *3.

    4. Reconnect the O70 radio receiver assembly connector*4.

    5. Reconnect the T20*2, *3 or T21*5 stereo component amplifier assembly connector.


      • *1: w/ Telematics Transceiver

      • *2: w/ Navigation System

      • *3: w/ Audio and Visual System with Parking Assist Monitor System

      • *4: w/ Audio and Visual System without Parking Assist Monitor System

      • *5: w/ Audio and Visual System without Parking Assist Monitor System (for 10 Speakers)

    6. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Proceed to
      OK
      NG

  7. Click here

    CONFIRM MODEL

    Result
    Result Proceed to
    w/ Navigation System A
    w/ Audio and Visual System with Parking Assist Monitor System
    w/ Audio and Visual System without Parking Assist Monitor System B

  8. Click here

    INSPECT RADIO RECEIVER ASSEMBLY (SHORT CIRCUIT IN RADIO RECEIVER ASSEMBLY)


    1. Reconnect the A78 ECM connector.

    2. Disconnect the O57 radio receiver assembly connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Result Proceed to
      OK A
      NG (w/ Telematics Transceiver) B
      NG (w/o Telematics Transceiver) C

  9. Click here

    INSPECT DCM (TELEMATICS TRANSCEIVER) (SHORT CIRCUIT IN DCM (TELEMATICS TRANSCEIVER))


    1. Reconnect the O57 radio receiver assembly connector.

    2. Disconnect the O65 DCM (Telematics Transceiver) connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

      If the result is as specified, there may be a short circuit in the DCM (Telematics Transceiver).

      Result
      Proceed to
      OK
      NG

  10. Click here

    INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (SHORT CIRCUIT IN STEREO COMPONENT AMPLIFIER ASSEMBLY)


    1. Reconnect the O65 DCM (Telematics Transceiver) connector.

    2. Disconnect the T20 stereo component amplifier assembly connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLYClick here

    • NG

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

  11. Click here

    INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (SHORT CIRCUIT IN STEREO COMPONENT AMPLIFIER ASSEMBLY)


    1. Reconnect the O57 radio receiver assembly connector.

    2. Disconnect the T20 stereo component amplifier assembly connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLYClick here

    • NG

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

  12. Click here

    INSPECT RADIO RECEIVER ASSEMBLY (SHORT CIRCUIT IN RADIO RECEIVER ASSEMBLY)


    1. Reconnect the A78 ECM connector.

    2. Disconnect the O70 radio receiver assembly connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Result Proceed to
      OK A
      NG (for 6 Speakers) B
      NG (for 10 Speakers) C

    • A

      REPLACE RADIO RECEIVER ASSEMBLYClick here

    • B

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    • CClick here
  13. Click here

    INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (SHORT CIRCUIT IN STEREO COMPONENT AMPLIFIER ASSEMBLY)


    1. Reconnect the O70 radio receiver assembly connector.

    2. Disconnect the T21 stereo component amplifier assembly connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O3-19 (+S) - Body ground Engine switch on (IG) 4.5 to 14 V
      Tip:

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

      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLYClick here

    • NG

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)