Lexus IS250 · Service Manual BODY ELECTRICAL

Operating Light Control Rheostat does not Change Light Brightness

Circuit diagnosis

DESCRIPTION

  1. The meter CPU receives signals for adjusting illumination on the meter and instrument panel from this circuit.
  2. The meter CPU detects the illumination level selected by the user according to the position of the rheostat knob.

HINT:
  1. This model is equipped with an Optitron meter, therefore the meter illuminates even in the daytime.
  2. The meter illumination level can be adjusted by turning the rheostat.
  3. The meter illumination dims when the light control switch is turned to the TAIL or HEAD position at night.
  4. Turning the rheostat knob fully clockwise cancels the above dimmer control.
  5. Turning the rheostat knob fully counterclockwise turns the meter illumination off.


WIRING DIAGRAM

E118068E01

INSPECTION PROCEDURE


1. SYSTEM CHECK

Result:
Result
 Proceed to
Meter illumination does not change when operate the light control rheostat knob
 A
Dimmer cancel does not operate
 B



B
Go to step 7
A


2. READ VALUE OF INTELLIGENT TESTER (RHEOSTAT VOL)

  1. Connect the intelligent tester to the DLC3.

  1. Engine switch on (IG).

  1. Turn the tester ON.

  1. Enter the following menus: Diagnosis / Body / Combination Meter / Data List.

  1. Check the values by referring to the table below.

    Combination Meter: 
    Item
    		 Measurement Item/Range (Display)
    		Normal Condition
    		 Diagnostic Note
    Light Control Rheostat
    		 Light control rheostat/Min.: 0, Max.: 255
    		 Light control rheostat switch is Dark (0) → Bright (255)
    		 -

    OK:
    The value displayed on the tester gradually changes as the actual rheostat operation.



 NG
Go to step 4
OK


3. READ VALUE OF INTELLIGENT TESTER (TAIL CANCEL SW)

  1. Connect the intelligent tester to the DLC3.

  1. Engine switch on (IG).

  1. Turn the tester ON.

  1. Enter the following menus: Diagnosis / Body / Combination Meter / Data List.

  1. Check the values by referring to the table below.

    Combination Meter: 
    Item
    		 Measurement Item/Range (Display)
    		Normal Condition
    		 Diagnostic Note
    Tail Cancel SW
    		 Tail cancel switch is ON/OFF
    		 ON: Light control rheostat turns fully clockwise
    OFF: Light control rheostat position is except above.
    		 -

    OK:
    Rheostat position displayed on the tester is same as the actual rheostat position.



 NG
Go to step 7
OK

REPLACE COMBINATION METER ASSEMBLY

4. INSPECT LIGHT CONTROL RHEOSTAT

  1. E123318E01
    Remove the light control rheostat with the connector still connected.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    E (J15-1) - RV (J15-4)
    		 Turn the rheostat knob fully clockwise
    		 8 to 12 kΩ
    E (J15-1) - RV (J15-4)
    		 Rheostat knob is between MIN. and MAX.
    		 The value changes gradually
    (Between approx. 0 to 8 kΩ)
    E (J15-1) - RV (J15-4)
    		 Turn the rheostat knob fully counterclockwise
    		 Approx. 0 Ω



NG
REPLACE LIGHT CONTROL RHEOSTAT
OK


5. CHECK HARNESS AND CONNECTOR (COMBINATION METER - LIGHT CONTROL RHEOSTAT)

  1. E118919E01
    Disconnect the J34 and J15 connectors.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J34-14 (ET) - J15-1 (E)
    		 Always
    		 Below 1 Ω
    J34-9 (ILL+) - J15-3 (T)
    		 Always
    		 Below 1 Ω
    J34-21 (TR) - J15-4 (RV)
    		 Always
    		 Below 1 Ω
    J15-1 (E) - Body ground
    		 Always
    		 10 kΩ or higher
    J15-3 (T) - Body ground
    		 Always
    		 10 kΩ or higher
    J15-4 (RV) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE COMBINATION METER ASSEMBLY

6. READ VALUE OF INTELLIGENT TESTER (TAIL CANCEL SW)

  1. Connect the intelligent tester to the DLC3.

  1. Engine switch on (IG).

  1. Turn the tester ON.

  1. Enter the following menus: Diagnosis / Body / Combination Meter / Data List.

  1. Check the values by referring to the table below.

    Combination Meter: 
    Item
    		 Measurement Item/Range (Display)
    		Normal Condition
    		 Diagnostic Note
    Tail Cancel SW
    		 Tail cancel switch is ON/OFF
    		 ON: Light control rheostat turns fully clockwise
    OFF: Light control rheostat position is except above.
    		 -

    OK:
    Rheostat position displayed on the tester is same as the actual rheostat position.



 NG
Go to step 7
OK

REPLACE COMBINATION METER ASSEMBLY

7. INSPECT LIGHT CONTROL RHEOSTAT

  1. E123318E02
    Remove the light control rheostat with connector still connected.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    T (J15-2) - TC (J15-3)
    		 Turn the rheostat knob fully counterclockwise
    		 Below 1 Ω
    T (J15-2) - TC (J15-3)
    		 Turn the rheostat knob fully clockwise
    		 10 kΩ or higher



NG
REPLACE LIGHT CONTROL RHEOSTAT
OK


8. CHECK HARNESS AND CONNECTOR (COMBINATION METER - LIGHT CONTROL RHEOSTAT)

  1. E118919E02
    Disconnect the J34 and J15 connectors.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J34-8 (TC) - J15-2 (TC)
    		 Always
    		 Below 1 Ω
    J15-2 (TC) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE COMBINATION METER ASSEMBLY


← Engine Coolant Temperature Receiver Gauge MalfunctionMeter Illumination is Always Dark →