Problem Symptoms Table [09/2020 - 11/2021]

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2024 Lexus IS 500, 2024 Lexus IS 350, 2024 Lexus IS 300, 2023 Lexus IS 500, and 2023 Lexus IS 350. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Before replacing the main body ECU (multiplex network body ECU), refer to Registration.
Refer to REGISTRATION [09/2020 - 11/2021]
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.
Refer to INITIALIZATION [09/2020 - ]
When replacing the headlight ECU sub-assembly LH, always replace it with a new one. If a headlight ECU sub-assembly LH which was installed to another vehicle is used, the information stored in it will not match the information from the vehicle and a DTC may be stored.
When replacing the combination meter assembly, always replace it with a new one. If a combination meter assembly which was installed to another vehicle is used, the information stored in it will not match the information from the vehicle and a DTC may be stored.
1. *: w/ Automatic Headlight Beam Level Control System

HINT:

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	Link
Left low beam headlight does not illuminate	Headlight unit assembly LH	Refer to DISASSEMBLY [09/2020 - ]
Left low beam headlight does not illuminate	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right low beam headlight does not illuminate	Headlight unit assembly RH	Refer to DISASSEMBLY [09/2020 - ]
Right low beam headlight does not illuminate	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Both left and right low beam headlights do not illuminate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
Both left and right low beam headlights do not illuminate	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
Left high beam headlight does not illuminate	High beam headlight circuit	Refer to High Beam Headlight Circuit [09/2020 - ]
Left high beam headlight does not illuminate	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right high beam headlight does not illuminate	High beam headlight circuit	Refer to High Beam Headlight Circuit [09/2020 - ]
Right high beam headlight does not illuminate	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Both left and right high beam headlights do not illuminate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
Both left and right high beam headlights do not illuminate	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
High Flash (passing function) does not operate (high beam headlights are normal)	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
Left low beam headlight and high beam headlight do not illuminate	Power source circuit	Refer to Power Source Circuit [09/2020 - ]
	Headlight unit assembly LH	Refer to DISASSEMBLY [09/2020 - ]
	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right low beam headlight and high beam headlight do not illuminate	Power source circuit	Refer to Power Source Circuit [09/2020 - ]
	Headlight unit assembly RH	Refer to DISASSEMBLY [09/2020 - ]
	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Left low beam headlight and high beam headlight flicker	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right low beam headlight and high beam headlight flicker	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]

PARKING LIGHT/DAYTIME RUNNING LIGHT

Symptom	Suspected Area	Link
Left parking light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
Left parking light does not illuminate	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right parking light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
Right parking light does not illuminate	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Both left and right parking lights do not illuminate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
Both left and right parking lights do not illuminate	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
Left daytime running light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
Left daytime running light does not illuminate	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right daytime running light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
Right daytime running light does not illuminate	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Both left and right daytime running lights do not illuminate	Check customize settings	Refer to CUSTOMIZE PARAMETERS [09/2020 - ]
	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
Left parking light/daytime running light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right parking light/daytime running light does not illuminate	Parking light/daytime running light circuit	Refer to Parking Light/Daytime Running Light Circuit [09/2020 - ]
	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Left parking light/daytime running light flicker	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right parking light/daytime running light flicker	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]

FRONT SIDE MARKER LIGHT

Symptom	Suspected Area	Link
Left front side marker light does not illuminate	Front side marker light circuit	Refer to Front Side Marker Light Circuit [09/2020 - ]
Left front side marker light does not illuminate	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right front side marker light does not illuminate	Front side marker light circuit	Refer to Front Side Marker Light Circuit [09/2020 - ]
Right front side marker light does not illuminate	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Both left and right front side marker lights do not illuminate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]
Left front side marker light flicker	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Right front side marker light flicker	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]

TAILLIGHT

Symptom	Suspected Area	Link
Left or right taillight (rear combination light assembly) does not illuminate	Rear combination light lens and body	Refer to INSPECTION [09/2020 - ]
	Harness or connector	-
Left or right taillight (rear light assembly) does not illuminate	Rear light lens and body	Refer to INSPECTION [09/2020 - ]
	Taillight LED	Refer to INSPECTION [09/2020 - ]
	Harness or connector	-
All of the taillights, license plate lights and rear side marker lights do not illuminate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
	Taillight relay circuit	Refer to Taillight Relay Circuit [09/2020 - ]
	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]

REAR SIDE MARKER LIGHT

Symptom	Suspected Area	Link
Left or right rear side marker light does not illuminate	Rear combination light lens and body	Refer to INSPECTION [09/2020 - ]

LICENSE PLATE LIGHT

Symptom	Suspected Area	Link
License plate light does not illuminate	License plate light assembly	Refer to INSPECTION [09/2020 - ]
License plate light does not illuminate	Harness or connector	-

STOP LIGHT

Symptom	Suspected Area	Link
Left or right stop light (rear combination light assembly) does not illuminate	Rear combination light lens and body	Refer to INSPECTION [09/2020 - ]
	Harness or connector	-
All of the stop lights do not illuminate	Stop light switch assembly	Refer to ON-VEHICLE INSPECTION [04/2013 - ]
	Semiconductor pwr integration ECU	Refer to REMOVAL [04/2013 - ]
	Harness or connector	-

HIGH MOUNTED STOP LIGHT

Symptom	Suspected Area	Link
High mounted stop light does not illuminate	Center stop light assembly	Refer to INSPECTION [04/2013 - ]
High mounted stop light does not illuminate	Harness or connector	-

BACK-UP LIGHT

Symptom	Suspected Area	Link
Left or right back-up light does not illuminate	Rear light lens and body	Refer to INSPECTION [09/2020 - ]
Left or right back-up light does not illuminate	Harness or connector	-
Both left and right back-up lights do not illuminate	Park/neutral position switch assembly (for A760H)	Refer to INSPECTION [04/2013 - ]
	Park/neutral position switch assembly (for AA81E)	Refer to INSPECTION [04/2013 - ]
	Instrument panel junction block assembly	Refer to REMOVAL [04/2013 - ]
	Harness or connector	-

TURN SIGNAL LIGHT

Symptom	Suspected Area	Link
Left or right front turn signal light does not operate*1	Headlight unit assembly	Refer to DISASSEMBLY [09/2020 - ]
	Headlight ECU sub-assembly	Refer to REMOVAL [09/2020 - ]
	Harness or connector	-
Left or right front turn signal light does not operate*2	Front turn signal light bulb	Refer to DISASSEMBLY [09/2020 - ]
	Headlight cord	Refer to DISASSEMBLY [09/2020 - ]
	Headlight unit assembly	Refer to DISASSEMBLY [09/2020 - ]
	Headlight ECU sub-assembly	Refer to REMOVAL [09/2020 - ]
	Harness or connector	-
Left or right side turn signal light does not operate	Side turn signal light assembly	Refer to INSPECTION [09/2020 - ]
	Outer mirror control ECU assembly*3	Refer to REMOVAL [04/2013 - ]
	Harness or connector	-
Left or right rear turn signal light does not operate	Rear combination light lens and body	Refer to INSPECTION [09/2020 - ]
Left or right rear turn signal light does not operate	Harness or connector	-
Turn signal lights do not operate in one direction	Turn signal switch circuit	Refer to Turn Signal Switch Circuit [09/2020 - ]
Turn signal lights do not operate in one direction	Meter/gauge system	Refer to HOW TO PROCEED WITH TROUBLESHOOTING [04/2013 - ]
All turn signal lights do not operate	Turn signal switch circuit	Refer to Turn Signal Switch Circuit [09/2020 - ]
	Windshield wiper switch assembly	Refer to REMOVAL [04/2013 - ]
	Combination meter assembly	Refer to REMOVAL [09/2020 - ]
All turn signal lights do not flash at the correct speed	Combination meter assembly	Refer to REMOVAL [09/2020 - ]

*1: for Triple Beam Headlight
*2: for Single Beam Headlight
*3: w/ Seat Position Memory

HAZARD WARNING SIGNAL LIGHT

Symptom	Suspected Area	Link
Hazard warning signal lights do not operate (turn signal lights are normal)	Hazard warning switch circuit	Refer to Hazard Warning Switch Circuit [09/2020 - ]
	Combination meter assembly	Refer to REMOVAL [09/2020 - ]
Hazard warning signal switch do not flash	Hazard warning signal switch (Air conditioning control assembly)	Refer to REMOVAL [04/2013 - ]
	Combination meter assembly	Refer to REMOVAL [09/2020 - ]
	Harness or connector	-

AUTOMATIC LIGHT CONTROL SYSTEM

Symptom	Suspected Area	Link
Automatic light control system does not operate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
Automatic light control system does not operate	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]

LIGHT AUTO TURN-OFF SYSTEM

Symptom	Suspected Area	Link
Light auto turn-off system does not operate	Headlight dimmer switch circuit	Refer to Headlight Dimmer Switch Circuit [09/2020 - ]
	IG signal circuit	Refer to IG Signal Circuit [04/2013 - ]
	Front Door courtesy switch circuit	Refer to Front Door Courtesy Switch Circuit [04/2013 - ]
	Rear Door courtesy switch circuit	Refer to Rear Door Courtesy Switch Circuit [04/2013 - ]
	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]

WELCOME LIGHT ILLUMINATION CONTROL

Symptom	Suspected Area	Link
Welcome light illumination control does not operate	Check customize settings	Refer to CUSTOMIZE PARAMETERS [09/2020 - ]
Welcome light illumination control does not operate	Main body ECU (Multiplex network body ECU)	Refer to REMOVAL [04/2013 - ]

AUTOMATIC HEADLIGHT BEAM LEVEL CONTROL SYSTEM (W/ AUTOMATIC HEADLIGHT BEAM LEVEL CONTROL SYSTEM)

Symptom	Suspected Area	Link
Automatic headlight beam level control system does not operate (Left Headlight)	Headlight beam level control actuator circuit	Refer to Headlight Beam Level Control Actuator Circuit [09/2020 - ]
	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]
Automatic headlight beam level control system does not operate (Right Headlight)	Headlight beam level control actuator circuit	Refer to Headlight Beam Level Control Actuator Circuit [09/2020 - ]
	Headlight ECU sub-assembly RH	Refer to REMOVAL [09/2020 - ]
Initialization cannot be performed	CAN communication system	Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2018 - ]
Initialization cannot be performed	Headlight ECU sub-assembly LH	Refer to REMOVAL [09/2020 - ]

AUTOMATIC HIGH BEAM SYSTEM

Symptom	Suspected Area	Link
Automatic high beam system does not operate or automatic high beam indicator light does not illuminate (low beam headlights and high beam headlights are normal)	Front radar sensor system	Refer to Automatic High Beam System does not Operate or Operation Indicator does not Illuminate [09/2020 - ]
	Check Data List (Front Recognition Camera High Temperature 2)
	Check automatic high beam indicator light
	Check Data List (Auto H Beam STS0)
	Perform Active Test (Automatic High Beam Indicator)
	Automatic high beam switch
	Harness or connector
	Combination meter assembly
	Forward recognition camera
	Main body ECU (Multiplex network body ECU)

REMOTE OPERATION FUNCTION (W/ TELEMATICS SYSTEM)

Symptom	Suspected Area	Link
Lights do not operate using remote operation function (Lighting system is normal)	Telematics system	Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2020 - ]