DESCRIPTION This circuit is necessary for the Automatic Sound Levelizer (ASL) built into the radio and display 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 on vehicle speed signals sent from the
combination meter assembly.
HINT:
- 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 its
respective system based on this 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
 CAUTION / NOTICE / HINT
NOTICE:
- Depending on the parts that are replaced during vehicle inspection or
maintenance, performing initialization, registration or calibration may
be needed. Refer to Precaution for Audio and Visual System.
Click here 
- When replacing the radio and display receiver assembly, always replace
it with a new one. If a radio and display receiver assembly which was
installed to another vehicle is used, the following may occur:
- A communication malfunction DTC may be stored.
- The radio and display receiver assembly may not operate normally.
PROCEDURE |
1. | CHECK VEHICLE SIGNAL (OPERATION CHECK) |
| (a) Enter the "Vehicle Signal Check Mode" screen. Refer to Check Vehicle Signal Check Mode in Operation Check.
Click here | |
(b)
While driving the vehicle, compare the value displayed for "SPEED" to
the reading on the speedometer. Check if these readings are almost
equal. HINT: The combination
meter assembly receives the vehicle speed signal from the skid control
ECU via CAN communication. Therefore, perform the following inspection
referring to values on the Data List of the skid control ECU because it
is the source of the vehicle speed signal. OK: Vehicle
speed displayed on the "Vehicle Signal Check Mode" screen is almost the
same as the actual vehicle speed measured using the Techstream. Click here
| OK |  |
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
|
NG |
 | |
| 2. |
INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM) |
| (a) Check the output waveform. (1) Remove the combination meter assembly with the connector still connected.
(2) Connect an oscilloscope to terminal G16-6 (+S) and body ground.
(3) Turn the power 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 |
G16-6 (+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. 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. |
 |
|
*a | Component with harness connected (Combination Meter Assembly) | | |
| NG |
| GO TO METER / GAUGE SYSTEM |
|
OK | |
| |
| 3. |
INSPECT RADIO AND DISPLAY RECEIVER ASSEMBLY (INPUT WAVEFORM) |
| (a) Check the input waveform. (1) Remove the radio and display receiver assembly with the connector still connected.
(2) Connect an oscilloscope to terminal G3-27 (SPD) and body ground.
(3) Turn the power 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 |
G3-27 (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. 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. |
 |
|
*a | Component with harness connected
(Radio and Display Receiver Assembly) | | |
| OK |
| REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY |
| NG |
| REPAIR OR REPLACE HARNESS OR CONNECTOR | |
