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 level in order to compensate for increased vehicle noise (vehicle noise tends to increase as vehicle speed increases). The ASL adjusts the volume level based upon vehicle speed signals that it receives from the combination meter assembly.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

   
   
   1. 

      Text in Illustration

      *a	Component with harness connected (Combination Meter Assembly)

      Check the output waveform.

      
      

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

      2. Connect an oscilloscope to terminal I18-3 (+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	I18-3 (+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.

   
   

   NG

   GO TO METER / GAUGE SYSTEM Click here

   OK

2. INSPECT RADIO RECEIVER ASSEMBLY (INPUT WAVEFORM)

   
   
   1. 

      Text in Illustration

      *a	Component with harness connected (Radio Receiver Assembly)

      Check the input waveform.

      
      

      1. Remove the radio receiver assembly with the connector still connected.

      2. Connect an oscilloscope to terminal I150-17 (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	I150-17 (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.

   
   

   NG

   CHECK HARNESS AND CONNECTOR (RADIO RECEIVER ASSEMBLY - JUNCTION CONNECTOR) Click here

   OK

   REPLACE RADIO RECEIVER ASSEMBLY Click here

3. CHECK HARNESS AND CONNECTOR (RADIO RECEIVER ASSEMBLY - JUNCTION CONNECTOR)

   
   

   1. Disconnect the I150 radio receiver assembly connector.

   2. Disconnect the I124 junction connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition I150-17 (SPD) - I124-17 Always Below 1 Ω

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR (RADIO RECEIVER ASSEMBLY - JUNCTION CONNECTOR)

   OK

4. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - JUNCTION CONNECTOR)

   
   

   1. Disconnect the I18 combination meter assembly connector.

   2. Disconnect the I124 junction connector connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition I18-3 (SPD) - I124-18 Always Below 1 Ω

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION CONNECTOR)