AUDIO / VIDEO: AUDIO AND VISUAL SYSTEM: Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter; 2018 - 2020 MY Sienna [11/2017

Last Modified: 04-05-2023	6.11:8.1.0	Doc ID: RM1000000018F8P
Model Year Start: 2018	Model: Sienna	Prod Date Range: [11/2017 - ]
Title: AUDIO / VIDEO: AUDIO AND VISUAL SYSTEM: Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter; 2018 - 2020 MY Sienna [11/2017 - ]

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 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.

for "Bluetooth":

Vehicle speed signals are sent 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.

HINT:

A voltage of 12 V or 5 V is output from each ECU connected to the combination meter assembly, 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 systems based on the pulse signal.
If a short occurs in any of the ECU or in the wire harness connected to an ECU, related components 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 occurs:
- A communication malfunction DTC may be stored.
- The radio and display receiver assembly may not operate normally.

PROCEDURE

1.	CHECK VEHICLE SIGNAL

(a) Enter the "Vehicle Signal Check Mode" screen. [Refer to Check Vehicle Signal Check Mode in Operation Check (See page )]

(b) While driving the vehicle, compare the value of "SPEED" to the reading on the speedometer.

(1) Check if these readings are almost equal.

OK:

Vehicle speed displayed on the "Vehicle Signal Check Mode" screen is almost the same as the reading on the speedometer.

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

(See page )

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 D145-3 (+S) and body ground.

(3) Turn the ignition switch to ON.

(4) Turn a wheel slowly.

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

Item	Condition
Measurement terminal	D145-3 (+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)

GO TO METER / GAUGE SYSTEM

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 D195-27 (SPD) and body ground.

(3) Turn the ignition switch to ON.

(4) Turn a wheel slowly.

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

Item	Condition
Measurement terminal	D195-27 (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)

REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY

GO TO METER / GAUGE SYSTEM