Toyota CH-R Service Manual: Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter

Toyota CH-R Service Manual / Audio / Video / Audio And Visual System(for Radio And Display Type) / 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 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.

HINT:

  • 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

PROCEDURE

1.

INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

(a) Check the output waveform.

(1) Remove the combination meter assembly with the connector still connected.

Click here

(2) Connect an oscilloscope to terminal F4-6 (+S) and body ground.

*a

Component with harness connected

(Combination Meter Assembly)

-

-

(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

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.

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.

NG

GO TO METER / GAUGE SYSTEM

OK

2.

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

(a) Disconnect the F129 radio and display receiver assembly connector.

(b) Disconnect the F4 combination meter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

F129-27 (SPD) - F4-6 (+S)

Always

Below 1 Ω

OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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