AUTOMATIC HEADLIGHT BEAM LEVEL CONTROL SYSTEM Speed Signal Circuit

DESCRIPTION

The headlight leveling ECU assembly receives the vehicle speed signal from the combination meter assembly.

Tech Tips


  • A voltage of 12 V or 5 V is output from each ECU and then input to the combination meter. The signal is changed to a pulse signal at the transistor in the combination meter. Each ECU controls the respective system 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


  1. A01I4U5E01

INSPECTION PROCEDURE

PROCEDURE


  1. CHECK COMBINATION METER SYSTEM


    1. The circuits that send vehicle speed signals to this system are inspected in the meter section Click here.

    2. During inspection for the meter system, if there is an instruction that indicates to go back to inspections for the lighting system, proceed to the next step.


    NEXT

  2. CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU ASSEMBLY - COMBINATION METER ASSEMBLY)


    1. Disconnect the I18 combination meter assembly connector.

    2. Disconnect the A34 headlight leveling ECU assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A34-16 (SPDR) - I18-3 (+S) Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)


    1. A01I41JE61
      Text in Illustration
      *a

      Component with harness connected

      (Combination Meter Assembly)

      Check the output waveform.


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

      2. Connect an oscilloscope to terminal I18-3 (+S) and body ground.

      3. Turn the power switch on (IG).

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

        Item Condition
        Tool setting 5 V/DIV., 20 ms./DIV.
        Vehicle condition Wheel being rotated
        OK
        The waveform is displayed 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

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