AUDIO AND VISUAL SYSTEM Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter

DESCRIPTION

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

Speed signals are received from the combination meter assembly (No. 3 meter circuit plate) and used for the ASL.

The ASL function automatically adjusts the sound volume in order to enable clear audio quality even when vehicle noise increases (as vehicle noise increases, the volume is turned up etc.).

Tech Tips


  • A voltage of 12 V or 5 V is output from each ECU and then input to the combination meter assembly (No. 3 meter circuit plate). 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

A01JCM7E01

INSPECTION PROCEDURE

PROCEDURE


  1. INSPECT COMBINATION METER ASSEMBLY (NO. 3 METER CIRCUIT PLATE (OUTPUT WAVEFORM))


    1. A01JBSEE21
      Text in Illustration
      *1

      Component with harness connected

      (Combination Meter Assembly (No. 3 Meter Circuit Plate))

      Check the output waveform.


      1. Remove the combination meter assembly (No. 3 meter circuit plate) with the connector still connected.

      2. Connect an oscilloscope to terminal L27-7 (+S) and body ground.

      3. Turn the power switch on (IG).

      4. Turn the wheel slowly.

      5. 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 Driving at approx. 20 km/h (12 mph)
        OK
        The waveform is displayed as 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.


    NG

    GO TO METER / GAUGE SYSTEM Click here

    OK

  2. CHECK HARNESS AND CONNECTOR (RADIO RECEIVER ASSEMBLY - COMBINATION METER ASSEMBLY)


    1. A01J8MRE15
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Radio Receiver Assembly)
      *2

      Front view of wire harness connector

      (to Combination Meter Assembly (No. 3 Meter Circuit Plate))

      Disconnect the radio receiver assembly and combination meter assembly (No. 3 meter circuit plate) connectors.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      L50-3 (SPD) - L27-7 (+S) Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE RADIO RECEIVER ASSEMBLY Click here