Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter

DESCRIPTION

for Automatic Sound Levelizer (ASL) (for 6 Speakers):

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 upon vehicle speed signals that it receives 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 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 assembly. The signal is changed to a pulse signal at the transistor in the combination meter assembly. 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 following diagram will not operate normally.

WIRING DIAGRAM

for 2AR-FE
for 2GR-FE

INSPECTION PROCEDURE

Note

After replacing the radio and display receiver assembly of vehicles subscribed to pay-type satellite radio broadcasts, XM radio ID registration is necessary (w/ SDARS System).

PROCEDURE

CHECK VEHICLE SIGNAL (OPERATION CHECK)

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

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

Tech Tips

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 (See page Click here).

NG

INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM) Click here

OK

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

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 I18-9 (+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
Measurement terminal	I18-9 (+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

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

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

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

Standard Resistance

Tester Connection	Condition	Specified Condition
I155-17 (SPD) - I18-9 (+S)	Always	Below 1 Ω

NG

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

OK

REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY Click here

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

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

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

Standard Resistance

Tester Connection	Condition	Specified Condition
I155-17 (SPD) - I124-17	Always	Below 1 Ω

NG

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

OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION CONNECTOR)

AUDIO AND VISUAL SYSTEM (for Radio and Display Type without Intuitive Parking Assist System) Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter