AUDIO AND VISUAL SYSTEM 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 and display 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 on vehicle speed signals sent from the combination meter sub-assembly*1, meter circuit plate*2.

for "Bluetooth":

Vehicle speed signals are sent from the combination meter sub-assembly*1, meter circuit plate*2 and used to cancel "Bluetooth" function operation.

The radio and display 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 sub-assembly*1 or meter circuit plate*2. The signal is changed to a pulse signal at the transistor in the combination meter sub-assembly*1 or meter circuit plate*2. 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.

*1: w/ TFT Display
*2: w/o TFT Display

WIRING DIAGRAM

PROCEDURE

CHECK VEHICLE SIGNAL (OPERATION CHECK)

Enter the "Vehicle Signal Check Mode" screen. Refer to Check Vehicle Signal in Operation Check Click here.

While driving the vehicle, compare the value displayed for "SPEED" to the reading on the speedometer. Check if these readings are almost equal.

Tech Tips

The combination meter sub-assembly*1 or meter circuit plate*2 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.

*1: w/ TFT Display
*2: w/o TFT Display

OK
Vehicle speed displayed on the "Vehicle Signal Check Mode" screen is almost the same as the actual vehicle speed measured using the GTS (See page Click here).

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

CHECK MODEL

Choose the model to be inspected.

Result

Result	Proceed to
w/ TFT Display	A
w/o TFT Display	B

INSPECT METER CIRCUIT PLATE (OUTPUT WAVEFORM) Click here

INSPECT COMBINATION METER SUB-ASSEMBLY (OUTPUT WAVEFORM)

Text in Illustration
*a	Component with harness connected (Combination Meter Sub-assembly)

Check the output waveform.

Remove the combination meter sub-assembly with the connector still connected.
Connect an oscilloscope to terminal L27-15 (+S) and body ground.
Turn the power switch on (IG).
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	L27-15 (+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.

GO TO METER / GAUGE SYSTEM Click here

INSPECT RADIO AND DISPLAY RECEIVER ASSEMBLY (INPUT WAVEFORM)

Check the input waveform.

Remove the radio and display receiver assembly with the connector still connected.
Connect an oscilloscope to terminal L35-17 (SPD) and body ground.
Turn the power switch on (IG).
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	L35-17 (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.

Text in Illustration
*a	Component with harness connected (Radio and Display Receiver Assembly)

REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY Click here

CHECK HARNESS AND CONNECTOR (RADIO AND DISPLAY RECEIVER ASSEMBLY - JUNCTION CONNECTOR)

Disconnect the L35 radio and display receiver assembly connector.
Disconnect the L70 junction connector.

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

Standard Resistance

for LHD
Tester Connection	Condition	Specified Condition
L35-17 (SPD) - L70-3	Always	Below 1 Ω

for RHD
Tester Connection	Condition	Specified Condition
L35-17 (SPD) - L70-12	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (COMBINATION METER SUB-ASSEMBLY - JUNCTION CONNECTOR)

Disconnect the L27combination meter sub-assembly connector.
Disconnect the L70 junction connector.

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

Standard Resistance

for LHD
Tester Connection	Condition	Specified Condition
L27-15 (+S) - L70-32	Always	Below 1 Ω

for RHD
Tester Connection	Condition	Specified Condition
L27-15 (+S) - L70-31	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION CONNECTOR)

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT METER CIRCUIT PLATE (OUTPUT WAVEFORM)

Text in Illustration
*a	Component with harness connected (Meter Circuit Plate)

Check the output waveform.

Remove the meter circuit plate with the connector still connected.
Connect an oscilloscope to terminal L27-15 (+S) and body ground.
Turn the power switch on (IG).
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	L27-15 (+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.

GO TO METER / GAUGE SYSTEM Click here

INSPECT RADIO AND DISPLAY RECEIVER ASSEMBLY (INPUT WAVEFORM)

Check the input waveform.

Remove the radio and display receiver assembly with the connector still connected.
Connect an oscilloscope to terminal L35-17 (SPD) and body ground.
Turn the power switch on (IG).
Turn a wheel slowly.

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

Item	Condition
Measurement terminal	L35-17 (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.

Text in Illustration
*a	Component with harness connected (Radio and Display Receiver Assembly)

REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY Click here

CHECK HARNESS AND CONNECTOR (RADIO AND DISPLAY RECEIVER ASSEMBLY - JUNCTION CONNECTOR)

Disconnect the L35 radio and display receiver assembly connector.
Disconnect the L70 junction connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
L35-17 (SPD) - L70-3	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (METER CIRCUIT PLATE - JUNCTION CONNECTOR)

Disconnect the L27 meter circuit plate connector.
Disconnect the L70 junction connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
L27-15 (+S) - L70-32	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION CONNECTOR)

REPAIR OR REPLACE HARNESS OR CONNECTOR