AUDIO AND VISUAL SYSTEM(for Radio Receiver Type) Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter

DESCRIPTION

for Automatic Sound Levelizer (ASL):

This circuit is necessary for the Automatic Sound Levelizer (ASL) built into the radio receiver assembly.

The Automatic Sound Levelizer (ASL) function automatically adjusts the audio system volume in order to compensate for increased vehicle noise (vehicle noise tends to increase as vehicle speed increases). The ASL adjusts the volume based upon vehicle speed signals sent from the combination meter assembly.

Tech Tips


  • A voltage of 12 V or 5 V is output from each ECU and then input to the combination meter assembly. The signal is changed to a pulse signal at the transistor in the combination meter assembly. Each ECU controls the respective system based on the pulse signal.

  • If a short occurs in any of the ECUs or in the wire harness connected to an ECU, all systems in the following diagram will not operate normally.

WIRING DIAGRAM

B0085KBE02
*1 to Other Systems
*2 Combination Meter Assembly
*3 Radio Receiver Assembly

PROCEDURE


  1. INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)


    1. Check the output waveform.

      B0089ILC02
      *a

      Component with harness connected

      (Combination Meter Assembly)

      		 - -

      1. Remove the combination meter assembly with the connector still connected.

      2. Connect an oscilloscope to terminal K21-6 (+S) and body ground.

      3. Turn the engine switch on (IG).

      4. Turn a wheel slowly.

      5. Check the signal waveform according to the condition(s) in the table below.

        Item Condition
        Measurement terminal K21-6 (+S) - Body ground
        Tool setting 5 V/DIV., 20 ms./DIV.
        Vehicle condition Wheel being rotated
        OK
        The waveform is similar to that shown in the illustration.

        Tech Tips

        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

    NG

    GO TO METER / GAUGE SYSTEM Click here

    OK

  2. INSPECT RADIO RECEIVER ASSEMBLY (INPUT WAVEFORM)


    1. Check the output waveform.

      B0083VOC54
      *a

      Component with harness connected

      (Radio Receiver Assembly)

      		 - -

      1. Remove the combination meter assembly with the connector still connected.

      2. Connect an oscilloscope to terminal K144-17 (SPD) and body ground.

      3. Turn the engine switch on (IG).

      4. Turn a wheel slowly.

      5. Check the signal waveform according to the condition(s) in the table below.

      Item Condition
      Measurement terminal K144-17 (SPD) - Body ground
      Tool setting 5 V/DIV., 20 ms./DIV.
      Vehicle condition Wheel being rotated
      OK
      The waveform is similar to that shown in the illustration.

      Tech Tips

      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 RADIO RECEIVER ASSEMBLY Click here

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR