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.

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.

for "Bluetooth":

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

The radio receiver 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. The signal is changed to a pulse signal at the transistor in the combination meter. 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 diagram below will not operate normally.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

Text in Illustration
*a	Component with harness connected (Combination Meter Assembly)

Check the output waveform.

Remove the combination meter assembly with the connector still connected.
Connect an oscilloscope to terminal E1-9 (+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
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

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

Disconnect the radio receiver connector and the combination meter assembly connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
E2-3 (SPD) - E1-9 (+S)	Always	Below 1 Ω

NG

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

OK

REPLACE RADIO RECEIVER Click here

CHECK HARNESS AND CONNECTOR (RADIO RECEIVER - JUNCTION CONNECTOR)

Disconnect the junction connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
E17-7 - E2-3 (SPD)	Always	Below 1 Ω

NG

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

OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION CONNECTOR)

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