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 sent from the combination meter assembly.

for "Bluetooth":

Vehicle speed signals are received from the combination meter assembly and used to cancel "Bluetooth" function operation.

The radio receiver assembly recognizes that the vehicle is being driven and makes it impossible to connect or register a "Bluetooth" device while driving.

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 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


*1	Other ECUs
*2	Radio Receiver Assembly
*3	Combination Meter Assembly

PROCEDURE

INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

Check the output waveform.

*a

Component with harness connected

(Combination Meter Assembly)

-

Remove the combination meter assembly with the connector still connected.
Connect an oscilloscope to terminal F4-6 (+S) and body ground.
Turn the ignition switch to ON.
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	F4-6 (+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 / DISPLAY Click here

OK

INSPECT RADIO RECEIVER ASSEMBLY (INPUT WAVEFORM)

Check the output waveform.

*a

Component with harness connected

(Radio Receiver Assembly)

-

Remove the combination meter assembly with the connector still connected.
Connect an oscilloscope to terminal F47-17 (SPD) and body ground.
Turn the ignition switch to ON.
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	F47-17 (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

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

Disconnect the F47 radio receiver assembly connector.
Disconnect the F4 combination meter assembly connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
F47-17 (SPD) - F4-6 (+S)	Always	Below 1 Ω

Result

Proceed to
OK
NG

OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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