Lexus IS250 IS220d GSE20 ALE20 - LIGHTING
READ VALUE OF INTELLIGENT TESTER
INSPECT HEADLIGHT DIMMER SWITCH ASSEMBLY
LIGHTING SYSTEM - Light Control Switch Circuit
DESCRIPTION
The combination switch ECU (windshield wiper switch assembly) receives the following switch information:
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
INSPECTION PROCEDURE
- HINT:
- Before starting the procedure, check that the multiplex communication system DTCs are not output .
1.READ VALUE OF INTELLIGENT TESTER |
Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG).
Turn the intelligent tester on.
Select the item(s) below in the DATA LIST, and read the display on the intelligent tester.
Item | Measurement Item / Display (Range) | Normal Condition | Diagnostic Note |
Rear Fog Light Switch | 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 | - |
Front Fog Light Switch | 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 Switch | 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 off | - |
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 | - |
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 | - |
Ignition Switch Signal | Engine switch signal / ON or OFF | ON: Engine switch on (IG) OFF: Engine switch off | - |
- OK:
- Condition information can be displayed.
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OK | ||
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2.INSPECT HEADLIGHT DIMMER SWITCH ASSEMBLY |
- HINT:
- Inspect the items that did not change as a result of monitoring the DATA LIST.

Remove the headlight dimmer switch assembly.
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
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OK | |
3.CHECK HARNESS AND CONNECTOR |

Disconnect the J26 windshield wiper switch assembly connector.
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
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
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OK | ||
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