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 stereo component amplifier assembly (No. 3 meter circuit plate) receives a vehicle speed signal from the combination meter assembly (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 combination meter assembly (No. 3 meter circuit plate). The signal is changed to a pulse signal at the transistor in the combination meter assembly (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 COMBINATION METER ASSEMBLY (NO. 3 METER CIRCUIT PLATE OUTPUT WAVEFORM)

(a) Check the output waveform.

(1) Remove the combination meter assembly 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. CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER - COMBINATION METER)

(a) Disconnect the L31 stereo component amplifier assembly connector.

(b) Disconnect the L27 combination meter assembly connector.

Text in Illustration

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

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

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

(a) Disconnect the L31 stereo component amplifier assembly connector.

(b) Disconnect the 4A No. 4 junction block connector.

Text in Illustration

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (STEREO COMPONENT AMPLIFIER - NO. 4 JUNCTION CONNECTOR)
OK -- Continue to next step.

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

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

(b) Disconnect the 3B No. 3 junction block connector.

Text in Illustration

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (NO. 4 JUNCTION CONNECTOR - NO. 3 JUNCTION CONNECTOR)
OK -- Continue to next step.

5. CHECK HARNESS AND CONNECTOR (NO. 3 JUNCTION CONNECTOR - COMBINATION METER ASSEMBLY)

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

(b) Disconnect the L27 combination meter assembly connector.

Text in Illustration

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (NO. 3 JUNCTION CONNECTOR - COMBINATION METER ASSEMBLY)
OK -- Continue to next step.

6. INSPECT NO. 4 JUNCTION BLOCK

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

Standard Resistance:

Text in Illustration

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

7. INSPECT NO. 3 JUNCTION BLOCK

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

Standard Resistance:

Text in Illustration

NG -- REPLACE NO. 3 JUNCTION BLOCK

OK -- REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY Removal