Vehicle Speed Signal Circuit Between Stereo Component Amplifier and Combination Meter

AUDIO / VISUAL: AUDIO AND VISUAL SYSTEM: Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter
- Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

DESCRIPTION

Audio function:

This circuit is necessary for the automatic sound levelizer (ASL) built into the stereo component amplifier assembly.

ASL function:

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

The ASL function automatically adjusts the sound in order to maintain clear audio sound 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 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





INSPECTION PROCEDURE

PROCEDURE

1. CHECK OPERATION OF SPEEDOMETER

(a) Drive the vehicle and check if the function of the speedometer on the combination meter assembly is normal.

OK:

Actual vehicle speed and the speed indicated on the speedometer are the same.

HINT
* The vehicle speed sensor is functioning normally when the indication on the speedometer is normal.
* The speed indicated on the speedometer has an allowable margin of error. This can be tested using a speedometer tester (calibrated chassis dynamometer). For details about testing and the margin of error, refer to "Operation Check" in the meter/gauge system Operation Check.

NG -- GO TO METER / GAUGE SYSTEM How To Proceed With Troubleshooting
OK -- Continue to next step.

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

(a) Disconnect the K15 stereo component amplifier assembly connector.





(b) Disconnect the J28 combination meter assembly connector.

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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. CHECK COMBINATION METER ASSEMBLY (SPEED SIGNAL)

(a) Check the input waveform.





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

(2) Connect an oscilloscope to terminal J28-35 (+S) and body ground.

(3) Turn the ignition switch to ON.

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

Measurement Condition





OK:

The waveform display is as shown in the illustration.

HINT
When the system is function normally, one wheel revolution generates 4 pulses.

As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

NG -- REPLACE COMBINATION METER ASSEMBLY Removal

OK -- REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY Removal