Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

AUDIO / VIDEO: AUDIO AND VISUAL SYSTEM (w/o Daytime Running Light): Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter
- Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

DESCRIPTION

The stereo component amplifier assembly receives a vehicle speed signal from the No. 3 meter circuit plate to control the ASL function.

HINT
* A voltage of 12 V or 5 V is output from each ECU and then input to the No. 3 meter circuit plate. The signal is changed to a pulse signal at the transistor in the No. 3 meter circuit plate. Each ECU controls the respective systems 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

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT NO. 3 METER CIRCUIT PLATE (OUTPUT WAVEFORM)

(a) Check the output waveform.

(1) Remove the No. 3 meter circuit plate with the connector(s) still connected.

(2) Connect an oscilloscope to terminal L27-7 (+S) and body ground.

(3) Turn the power switch on (IG).

(4) Turn a wheel slowly.

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

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.

Text in Illustration

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

2. INSPECT STEREO COMPONENT AMPLIFIER ASSEMBLY (INPUT WAVEFORM)

(a) Check the input waveform.

(1) Remove the stereo component amplifier assembly with the connector(s) still connected.

(2) Connect an oscilloscope to terminal L143-11 (SPD) and body ground.

(3) Turn the power switch on (IG).

(4) Turn a wheel slowly.

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

NG -- CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY - NO. 3 METER CIRCUIT PLATE)

OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Problem Symptoms Table

3. CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY - NO. 3 METER CIRCUIT PLATE)

(a) Disconnect the stereo component amplifier assembly connector.

(b) Disconnect the No. 3 meter circuit plate connector.

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

Standard Resistance:

NG -- CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY - NO. 4 JUNCTION BLOCK)

OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Problem Symptoms Table

4. CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY - NO. 4 JUNCTION BLOCK)

(a) Disconnect the stereo component amplifier assembly connector.

(b) Disconnect the No. 4 junction block 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.

5. CHECK HARNESS AND CONNECTOR (NO. 3 JUNCTION BLOCK - NO. 4 JUNCTION BLOCK)

(a) Disconnect the No. 3 junction block connector.

(b) Disconnect the No. 4 junction block 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.

6. CHECK NO. 4 JUNCTION BLOCK

(a) Disconnect the No. 4 junction block connector.

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

Standard Resistance:

NG -- REPLACE NO. 4 JUNCTION BLOCK
OK -- Continue to next step.

7. CHECK NO. 3 JUNCTION BLOCK

(a) Disconnect the No. 3 junction block connector.

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

Standard Resistance:

NG -- REPLACE NO. 3 JUNCTION BLOCK

OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (NO. 3 METER CIRCUIT PLATE - NO. 3 JUNCTION BLOCK)