Lexus IS250 · Service Manual BODY ELECTRICAL

Light Control Switch Circuit

Circuit diagnosis

DESCRIPTION

The combination switch ECU (windshield wiper switch assembly) receives the following switch information.
  1. Light control switch position is Off, Tail, Head, or Auto
  2. Headlight dimmer switch position is High, Low, or Flash (Pass)
  3. Turn signal switch position is LH, RH or Off
  4. Fog light switch position is On or Off
The combination switch ECU then converts these signals to BEAN signals and sends them to each ECU via the multiplex communication system.
The headlight dimmer switch assembly includes the light control, headlight dimmer, turn signal, and fog light switches.

WIRING DIAGRAM

E125739E01
E125739E02

INSPECTION PROCEDURE

HINT:
Before starting the procedure, check that the multiplex communication system DTCs are not output (Click here).


1. READ VALUE OF INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Turn the intelligent tester on.

  1. Select the item(s) in the DATA LIST, and read the display on the intelligent tester.

    DATA LIST: COMBI SW (Combination Switch ECU) 
    Item
    		 Measurement Item / Display
    (Range)
    		 Normal Condition
    		 Diagnostic Note
    Front Fog Light SW
    		 Front fog light switch signal / ON or OFF
    		 ON: Front fog light switch is in ON position
    OFF: Front fog light switch is not in ON position
    		 -
    Passing Light SW
    		 Passing light switch signal / ON or OFF
    		ON: Headlight dimmer switch is in FLASH (PASS) position
    OFF: Headlight dimmer switch is not in FLASH (PASS) position
    		 -
    Dimmer HI Switch
    		 High beam switch signal / ON or OFF
    		 ON: Headlight dimmer switch is in HI position
    OFF: Headlight dimmer switch is not in HI position
    		 -
    Light Auto Switch
    		 Auto light switch signal / ON or OFF
    		 ON: Light control switch is in AUTO position
    OFF: Light control switch is not in AUTO position
    		 -
    Head Light Switch
    		 Headlight control switch signal / ON or OFF
    		 ON: Light control switch is in HEAD position
    OFF: Light control switch is not in HEAD position
    		 -
    Tail Light Switch
    		 Taillight switch signal / ON or OFF
    		 ON: Light control switch is in TAIL or HEAD position
    OFF: Light control switch is not in OFF position
    		 -
    Turn Left Switch
    		 Turn signal switch LH signal / ON or OFF
    		 ON: Light control switch is in LH position
    OFF: Light control switch is not in LH position
    		 -
    Rear Fog Light SW
    		 Rear fog light switch signal / ON or OFF
    		 ON: Rear fog light switch is in ON position
    OFF: Rear fog light switch is not in ON position
    		 -
    Turn Right Switch
    		 Turn signal switch RH signal / ON or OFF
    		 ON: Light control switch is in RH position
    OFF: Light control switch is not in RH position
    		 -
    IG Switch Signal
    		 Engine switch signal / ON or OFF
    		 ON: Engine switch on (IG)
    OFF: Engine switch off
    		 -

    OK:
    Condition information can be displayed.



 NG
Go to step 2
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

2. INSPECT HEADLIGHT DIMMER SWITCH ASSEMBLY

HINT:
Inspect the items that did not change as a result of monitoring the DATA LIST.

  1. E123258E01
    Remove the headlight dimmer switch assembly.

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

    Standard resistance:
    Light Control Switch (LHD, RHD light control switch LH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-12 (EL) - f1-18 (T)
    		 OFF
    		 10 kΩ or higher
    f1-18 (T) - f1-19 (AUTO)
    		OFF
    		 10 kΩ or higher
    f1-19 (AUTO) - f1-20 (H)
    		OFF
    		 10 kΩ or higher
    f1-12 (EL) - f1-18 (T)
    		TAIL
    		 Below 1 Ω
    f1-12 (EL) - f1-18 (T)
    		HEAD
    		 Below 1 Ω
    f1-18 (T) - f1-20 (H)
    		HEAD
    		 Below 1 Ω
    f1-12 (EL) - f1-19 (AUTO)
    		 AUTO
    		 Below 1 Ω
    Light Control Switch (RHD light control switch RH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-19 (EL) - f1-13 (T)
    		 OFF
    		 10 kΩ or higher
    f1-13 (T) - f1-12 (AUTO)
    		OFF
    		 10 kΩ or higher
    f1-12 (AUTO) - f1-11 (H)
    		OFF
    		 10 kΩ or higher
    f1-19 (EL) - f1-13 (T)
    		TAIL
    		 Below 1 Ω
    f1-19 (EL) - f1-13 (T)
    		HEAD
    		 Below 1 Ω
    f1-13 (T) - f1-11 (H)
    		HEAD
    		 Below 1 Ω
    f1-19 (EL) - f1-12 (AUTO)
    		 AUTO
    		 Below 1 Ω
    Headlight Dimmer Switch (LHD, RHD light control switch LH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-11 (HU) - f1-12 (EL)
    		 LOW BEAM
    		 Below 1 Ω
    f1-11 (HU) - f1-12 (EL)
    		 HI BEAM
    		 Below 1 Ω
    f1-12 (EL) - f1-17 (HF)
    		 HI BEAM
    		 Below 1 Ω
    Headlight Dimmer Switch (RHD light control switch RH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-15 (HU) - f1-19 (EL)
    		 LOW BEAM
    		 Below 1 Ω
    f1-15 (HU) - f1-19 (EL)
    		 HI BEAM
    		 Below 1 Ω
    f1-19 (EL) - f1-14 (HF)
    		 HI BEAM
    		 Below 1 Ω
    Turn Signal Switch (LHD, RHD light control switch LH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-12 (EL) - f1-13 (TR)
    		 Right turn
    		 Below 1 Ω
    f1-12 (EL) - f1-13 (TR)
    		 Neutral
    		 10 kΩ or higher
    f1-12 (EL) - f1-15 (TL)
    		 Neutral
    		 10 kΩ or higher
    f1-12 (EL) - f1-15 (TL)
    		 Left turn
    		 Below 1 Ω
    Turn Signal Switch (RHD light control switch RH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-19 (EL) - f1-16 (TR)
    		 Right turn
    		 Below 1 Ω
    f1-19 (EL) - f1-16 (TR)
    		 Neutral
    		 10 kΩ or higher
    f1-19 (EL) - f1-18 (TL)
    		 Neutral
    		 10 kΩ or higher
    f1-19 (EL) - f1-18 (TL)
    		 Left turn
    		 Below 1 Ω
    Fog Light Switch (LHD, RHD light control switch LH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-3 (LFG) - f1-4 (BFG)
    		 OFF
    		 10 kΩ or higher
    f1-4 (BFG) - f1-2 (B)
    		 OFF
    		 10 kΩ or higher
    f1-3 (LFG) - f1-2 (B)
    		 OFF
    		 10 kΩ or higher
    f1-3 (LFG) - f1-4 (BFG)
    		 Front fog light switch ON
    		 Below 1 Ω
    f1-3 (LFG) - f1-4 (BFG)
    		 Rear fog light switch ON
    		 Below 1 Ω
    f1-4 (BFG) - f1-2 (B)
    		 Rear fog light switch ON
    		 Below 1 Ω
    f1-3 (LFG) - f1-2 (B)
    		 Rear fog light switch ON
    		 Below 1 Ω
    Fog Light Switch (RHD light control switch RH side type):
    Tester Connection
    		 Switch Condition
    		 Specified Condition
    f1-8 (LFG) - f1-7 (BFG)
    		 OFF
    		 10 kΩ or higher
    f1-7 (BFG) - f1-9 (RFG)
    		 OFF
    		 10 kΩ or higher
    f1-8 (LFG) - f1-9 (RFG)
    		 OFF
    		 10 kΩ or higher
    f1-8 (LFG) - f1-7 (BFG)
    		 Front fog light switch ON
    		 Below 1 Ω
    f1-8 (LFG) - f1-7 (BFG)
    		 Rear fog light switch ON
    		 Below 1 Ω
    f1-7 (BFG) - f1-9 (RFG)
    		 Rear fog light switch ON
    		 Below 1 Ω
    f1-8 (LFG) - f1-9 (RFG)
    		 Rear fog light switch ON
    		 Below 1 Ω



NG
REPLACE HEADLIGHT DIMMER SWITCH ASSEMBLY
OK


3. CHECK HARNESS AND CONNECTOR

  1. E108738E05
    Disconnect the J26 windshield wiper switch assembly connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J26-5 (E) - Body ground
    		Always
    		 Below 1 Ω

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    J26-1 (B) - J26-5 (E)
    		 Always
    		 10 to 14 V
    J26-2 (IG) - J26-5 (E)
    		 Engine switch on (IG)
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE WINDSHIELD WIPER SWITCH ASSEMBLY


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