LIGHTING SYSTEM PROBLEM SYMPTOMS TABLE

Note

Before replacing the main body ECU (multiplex network body ECU), refer to Precaution Click here.
If the headlight ECU sub-assembly LH has been replaced, it is necessary to synchronize the vehicle information and initialize the headlight ECU sub-assembly LH. Click here.

Tech Tips

Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.

Headlight
Symptom	Suspected Area	See page
Left low beam headlight does not illuminate	Headlight unit assembly LH (for Triple Beam Headlight)	Click here
	Headlight unit assembly LH (for Single Beam Headlight)	Click here
	Headlight unit LH (for Triple Beam Headlight)	Click here
	Headlight unit LH (for Single Beam Headlight)	Click here
	Headlight ECU sub-assembly LH	Click here
	Harness or connector	-
Right low beam headlight does not illuminate	Headlight unit assembly RH (for Triple Beam Headlight)	Click here
	Headlight unit assembly RH (for Single Beam Headlight)	Click here
	Headlight unit RH (for Triple Beam Headlight)	Click here
	Headlight unit RH (for Single Beam Headlight)	Click here
	Headlight ECU sub-assembly RH	Click here
	Harness or connector	-
Both left and right low beam headlights do not illuminate	Headlight dimmer switch circuit	Click here
Both left and right low beam headlights do not illuminate	Main body ECU (Multiplex network body ECU)	Click here
Left high beam headlight does not illuminate (for Single Beam Headlight)	High beam headlight circuit	Click here
Left high beam headlight does not illuminate (for Triple Beam Headlight)	Headlight unit assembly LH	Click here
	Headlight unit LH	Click here
	Headlight ECU sub-assembly LH	Click here
Right high beam headlight does not illuminate (for Single Beam Headlight)	High beam headlight circuit	Click here
Right high beam headlight does not illuminate (for Triple Beam Headlight)	Headlight unit assembly RH	Click here
	Headlight unit RH	Click here
	Headlight ECU sub-assembly RH	Click here
Both left and right high beam headlights do not illuminate	Headlight dimmer switch circuit	Click here
Both left and right high beam headlights do not illuminate	Main body ECU (Multiplex network body ECU)	Click here
High Flash (passing function) does not operate (high beam headlights are normal)	Headlight dimmer switch circuit	Click here
	Main body ECU (Multiplex network body ECU)	Click here
Left low beam headlight, high beam headlight, front side marker light, daytime running light and parking light do not illuminate	Power source circuit	Click here
	Headlight ECU sub-assembly LH	Click here
Right low beam headlight, high beam headlight, front side marker light, daytime running light and parking light do not illuminate	Power source circuit	Click here
	Headlight ECU sub-assembly RH	Click here

Clearance Light
Symptom	Suspected Area	See page
Left clearance light does not illuminate	Clearance Light/Daytime running light circuit	Click here
Left clearance light does not illuminate	Headlight ECU sub-assembly LH	Click here
Right clearance light does not illuminate	Clearance Light/Daytime running light circuit	Click here
Right clearance light does not illuminate	Headlight ECU sub-assembly RH	Click here
Both left and right clearance lights do not illuminate	Headlight dimmer switch circuit	Click here
Both left and right clearance lights do not illuminate	Main body ECU (Multiplex network body ECU)	Click here

Daytime Running Light
Symptom	Suspected Area	See page
Left daytime running light does not illuminate	Clearance Light/Daytime running light circuit	Click here
Left daytime running light does not illuminate	Headlight ECU sub-assembly LH	Click here
Right daytime running light does not illuminate	Clearance Light/Daytime running light circuit	Click here
Right daytime running light does not illuminate	Headlight ECU sub-assembly RH	Click here
Both left and right daytime running lights do not illuminate	CAN communication system (for LHD)	Click here
	CAN communication system (for RHD)	Click here
	Check customize settings	Click here
	Electric parking brake system	Click here
	Headlight dimmer switch circuit	Click here
	Main body ECU (Multiplex network body ECU)	Click here
	Harness or connector	-

Taillight
Symptom	Suspected Area	See page
Left or right taillight and rear side marker light (rear combination light assembly) do not illuminate	Rear combination light assembly	Click here
	Rear combination light socket and wire	Click here
	Harness or connector	-
Left or right taillight (rear light assembly) does not illuminate	Rear light assembly	Click here
	Rear light socket and wire	Click here
	Harness or connector	-
All of the taillights, license plate lights and rear side marker lights do not illuminate	Headlight dimmer switch circuit	Click here
	Taillight relay circuit	Click here
	Harness or connector	-
	No. 2 integration relay	Click here
	Main body ECU (Multiplex network body ECU)	Click here

License Plate Light
Symptom	Suspected Area	See page
Left or right license plate light does not illuminate	License plate light assembly	Click here
Left or right license plate light does not illuminate	Harness or connector	-

Stop Light
Symptom	Suspected Area	See page
Left or right stop light (rear combination light assembly) does not illuminate	Rear combination light assembly	Click here
	Harness or connector	-
Left or right stop light (rear light assembly) does not illuminate	Rear light assembly	Click here
	Harness or connector	-
Center stop light does not illuminate	Center stop light assembly	Click here
Center stop light does not illuminate	Harness or connector	-
All of the stop lights do not illuminate	STOP fuse	-
	Stop light switch assembly	Click here
	No. 2 integration relay*	Click here
	Harness or connector	-

External Lights
Symptom	Suspected Area	See page
Stop lights, taillights, and fog lights do not illuminate	No. 2 integration relay*	Click here
	Harness or connector	-
	Main body ECU (Multiplex network body ECU)	Click here

Tech Tips

*: If the DTCs indicate that there is a malfunction, there may be a problem with the following parts.

Wire harness or connector between No. 2 integration relay and load (each stop light)
Rear combination light assembly, rear light assembly or center stop light assembly
No. 2 integration relay

Front Fog Light (w/ Front Fog Light)
Symptom	Suspected Area	See page
Front fog light does not illuminate (taillight is normal).	Front fog light assembly	Click here
	Headlight dimmer switch circuit	Click here
	Front fog light circuit	Click here
	Harness or connector	-
	No. 2 integration relay	Click here
	Main body ECU (Multiplex network body ECU)	Click here

Rear Fog Light (w/ Rear Fog Light)
Symptom	Suspected Area	See page
Rear fog light does not illuminate (taillight is normal).	RR FOG fuse	-
	Headlight dimmer switch circuit	Click here
	Rear fog light circuit	Click here
	Harness or connector	-
	Rear light lens and body LH (for LHD)	Click here
	Rear light lens and body RH (for RHD)	Click here
	Main body ECU (Multiplex network body ECU)	Click here

Back-up Light
Symptom	Suspected Area	See page
Left or right back-up light does not illuminate	Rear light assembly	Click here
Left or right back-up light does not illuminate	Harness or connector	-
Both left and right back-up lights do not illuminate	Hybrid control system	Click here
	BACK UP fuse	-
	IGCT NO.1 fuse	-
	IGCT NO.5 fuse	-
	IGCT relay	-
	No. 1 junction block assembly (BACK UP relay)	-
	Shift lever position sensor (for L110)	Click here
	Shift lever position sensor (for L210)	Click here
	Power management control ECU	Click here
	Harness or connector	-

Turn Signal Light
Symptom	Suspected Area	See page
Headlight dimmer switch does not operate normally	Windshield wiper switch assembly	Click here
	Headlight dimmer switch	Click here
	Steering angle sensor	Click here
	Harness or connector	-
All turn signal lights do not operate	Turn signal switch circuit	Click here
	Windshield wiper switch assembly	Click here
	Combination meter assembly	Click here
All turn signal lights do not flash at the correct speed	Combination meter assembly	Click here

Hazard Warning Signal Light
Symptom	Suspected Area	See page
Hazard warning signal lights do not operate	Hazard warning switch circuit	Click here
Hazard warning signal lights do not operate	Combination meter assembly	Click here
Hazard warning signal switch indicator does not illuminate	HAZ fuse	-
	Multi-media module receiver assembly (hazard warning signal switch)	Click here
	Combination meter assembly	Click here
	Harness or connector	-

Automatic Light Control System
Symptom	Suspected Area	See page
Automatic light control system does not operate	Check DTCs	Click here
	Headlight dimmer switch circuit	Click here
	IG signal circuit	Click here
	Main body ECU (Multiplex network body ECU)	Click here

Light Auto Turn-off System
Symptom	Suspected Area	See page
Light auto turn-off system does not operate	Headlight dimmer switch circuit	Click here
	IG signal circuit	Click here
	Door courtesy switch circuit	Click here
	Main body ECU (Multiplex network body ECU)	Click here

Lexus Enform Remote Services
Symptom	Suspected Area	See page
Lexus Enform Remote does not operate (lighting system is normal).	Telematics system (w/ Telematics Transceiver for G-BOOK)	Click here
	Telematics system (w/ Telematics Transceiver except G-BOOK)	Click here