AIR CONDITIONING SYSTEM (for Automatic Air Conditioning System) Vehicle Speed Signal Circuit

CAUTION / NOTICE / HINT

DESCRIPTION

The air conditioning amplifier assembly monitors signals from the speedometer sensor via the combination meter assembly. The air conditioning amplifier assembly uses these signals to adjust the thermistor signal.

WIRING DIAGRAM

A01J3YIE04

INSPECTION PROCEDURE

Tech Tips

Check that the speedometer in the combination meter assembly operates normally before inspecting the vehicle speed signal circuit Click here.

PROCEDURE


  1. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY


    1. A01J7A5E08
      Text in Illustration
      *a

      Component with harness connected

      (Air Conditioning Amplifier Assembly)

      Remove the air conditioning amplifier assembly with its connectors still connected Click here.

    2. Using an oscilloscope, check the waveform of the air conditioning amplifier assembly.

      Measurement Condition
      Item Content
      Tester Connection A38-9 (SPD) - Body ground
      Tool Setting 5 V/DIV., 20 ms./DIV.
      Condition Driving at approximately 20 km/h (12 mph)
      OK
      Waveform is as shown in the illustration.

      Tech Tips

      As the vehicle speed increases, the wavelength becomes shorter.


    NG

    CHECK COMBINATION METER ASSEMBLY Click here

    OK

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

  2. CHECK COMBINATION METER ASSEMBLY


    1. A01J6KUE06
      Text in Illustration
      *a

      Component with harness connected

      (Combination Meter Assembly)

      Remove the combination meter assembly with its connector still connected Click here.

    2. Connect an oscilloscope to the combination meter assembly connector.

    3. Check the waveform.

      Measurement Condition
      Item Content
      Tester Connection C27-6 - Body ground
      Tool setting 5 V/DIV., 20 ms./DIV.
      Condition Vehicle is driven at approximately 20 km/h (12 mph)
      OK
      Waveform is as 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.


    NG

    REPLACE COMBINATION METER ASSEMBLY Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (COMBINATION METER - AIR CONDITIONING AMPLIFIER)


    1. Disconnect the C27 combination meter assembly connector.

    2. Disconnect the A38 air conditioning amplifier assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      C27-6 - A38-9 (SPD) Always Below 1 Ω
      A38-9 (SPD) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here