Vehicle Speed Signal Circuit Between Stereo Component Amplifier and Combination Meter

AUDIO / VISUAL: AUDIO AND VISUAL SYSTEM (w/ Navigation System for HDD): Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter
- Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

DESCRIPTION

The circuit is necessary for the Automatic Sound Levelizer (ASL) built into the stereo component amplifier assembly.

Speed signals are received from the combination meter assembly and used for the ASL.

The ASL function automatically adjusts the sound volume in order to clear audio quality even when vehicle noise increases (as vehicle noise increases, the volume is turned up etc.).

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 diagram below will not operate normally.
WIRING DIAGRAM





INSEPCTION PROCEDURE

PROCEDURE

1. 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 C8-21 (+S) and body ground.

(3) Turn the ignition switch to ON.

(4) Turn the wheel slowly.

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





OK:

The waveform is displayed as shown in the illustration.

Text in Illustration





NG -- GO TO METER / GAUGE SYSTEM
OK -- Continue to next step.

2. CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY - COMBINATION METER)

(a) Disconnect the stereo component amplifier assembly connector and combination meter assembly connector.

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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY Service and Repair