DESCRIPTION
The stereo component amplifier assembly receives a vehicle speed signal from the combination meter assembly to control the ASL function.
Tech Tips
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 its respective systems based on this 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 | to Other Systems |
*2 | Combination Meter Assembly |
*3 | Stereo Component Amplifier Assembly |
PROCEDURE
INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)
*a | Component with harness connected (Combination Meter Assembly) |
Check the output waveform.
Remove the combination meter assembly with the connector(s) still connected.
Connect an oscilloscope to terminal O3-19 (+S) and body ground.
Turn the engine switch on (IG).
Turn a wheel slowly.
Check the signal waveform according to the condition(s) in the table below.
Item | Condition |
---|---|
Measurement terminal | O3-19 (+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. |
Tech Tips
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.
Result | |||
---|---|---|---|
|
NG |
GO TO METER / GAUGE SYSTEM Click here |
OK |
INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (INPUT WAVEFORM)
*a | Component with harness connected (Stereo Component Amplifier Assembly) |
Check the input waveform.
Remove the stereo component amplifier assembly with the connector(s) still connected.
Connect an oscilloscope to terminal T20-17 (SPD) and body ground.
Turn the engine switch on (IG).
Turn a wheel slowly.
Check the signal waveform according to the condition(s) in the table below.
Item | Condition |
---|---|
Measurement terminal | T20-17 (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. |
Tech Tips
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.
Result | |||
---|---|---|---|
|
OK |
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here |
NG |
REPAIR OR REPLACE HARNESS OR CONNECTOR (COMBINATION METER ASSEMBLY - STEREO COMPONENT AMPLIFIER ASSEMBLY) |