Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

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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.
Speed signals are received from the combination meter 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. The signal is changed to a pulse signal at the transistor in the combination meter. 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

1. for 2GR-FE





2. for 1AR-FE





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT COMBINATION METER (OUTPUT WAVEFORM)




(a) Check the output waveform.
(1) Remove the combination meter with the connector still connected.
(2) Connect an oscilloscope to terminal E1-16 (+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.
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.

Text in Illustration





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

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




(a) Disconnect the stereo component amplifier and combination meter connectors.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:





Text in Illustration





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE STEREO COMPONENT AMPLIFIER