Lexus NX: Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

Lexus NX Service Manual / Audio & Visual & Telematics / Audio / Video / Audio And Visual System / Vehicle Speed Signal Circuit between Stereo Component Amplifier and Combination Meter

DESCRIPTION

The stereo component amplifier assembly receives a vehicle speed signal from the combination meter assembly 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. 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 diagram below will not operate normally.

WIRING DIAGRAM

PROCEDURE

1.

CHECK COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

(a) Check the output waveform.

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

(2) Connect an oscilloscope to terminal I10-19 (+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.

Item

Condition

Measurement terminal

I10-19 (+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.

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.

*a

Component with harness connected

(Combination Meter Assembly)

NG

GO TO METER / GAUGE SYSTEM

OK

2.

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

(a) Disconnect the P46 stereo component amplifier assembly connector.

(b) Disconnect the I10 combination meter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

P46-11 (SPD) - I10-19 (+S)

Always

Below 1 Ω

OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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