Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Headlight LH Circuit (B2439,B243A)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Exterior / Lighting (ext) / Lighting System (w/ Automatic Headlight Beam Level Control System) / Headlight LH Circuit (B2439,B243A)

DESCRIPTION

The No. 1 headlight ECU sub-assembly LH and No. 1 headlight ECU sub-assembly RH internally boost the power supply voltage to ensure a constant supplied current for the lo/hi beam LED of their respective headlight.

By monitoring the LED power supply voltage, abnormal current and malfunctions can be detected.

for Multiple Beam Headlight

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

DTC Output from

B2439

Headlight LH Circuit
  • All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on
Malfunction status:
  • Headlight unit malfunction
  • Open/short in Lo/Hi beam circuit
  • 1 seconds or more
  • No. 1 headlight ECU sub-assembly LH
  • Headlight unit LH

AFS

B243A

Headlight RH Circuit
  • All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on
Malfunction status:
  • Headlight unit malfunction
  • Open/short in Lo/Hi beam circuit
  • 10 seconds or more
  • No. 1 headlight ECU sub-assembly RH
  • Headlight unit RH

AFS
for Single Beam Headlight

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

DTC Output from

B2439

Headlight LH Circuit
  • All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on
Malfunction status:
  • Headlight unit malfunction
  • Open/short in Lo/Hi beam circuit
  • 1 seconds or more
  • No. 1 headlight ECU sub-assembly LH
  • Headlight unit LH

HL AutoLeveling

B243A

Headlight RH Circuit
  • All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on
Malfunction status:
  • Headlight unit malfunction
  • Open/short in Lo/Hi beam circuit
  • 10 seconds or more
  • No. 1 headlight ECU sub-assembly RH
  • Headlight unit RH

HL AutoLeveling

WIRING DIAGRAM

for Multiple Beam Headlight

for Single Beam Headlight

CAUTION / NOTICE / HINT

NOTICE:

  • If the No. 1 headlight ECU sub-assembly LH has been replaced, it is necessary to synchronize the vehicle information and initialize the No. 1 headlight ECU sub-assembly LH.

    Click here

  • If the headlight assembly LH has been replaced, it is necessary to synchronize the vehicle information and initialize the No. 1 headlight ECU sub-assembly LH.*

    Click here

  • When replacing the No. 1 headlight ECU sub-assembly LH, always replace it with a new one. If a No. 1 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 headlight assembly LH, always replace it with a new one. If a headlight 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.*
    • *: for TMMC Made

PROCEDURE

1.

CONFIRM MODEL

(a) Choose the model to be inspected.

Result

Proceed to

for Multiple Beam Headlight

A

for Single Beam Headlight

B
B

GO TO STEP 10

A

2.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > AFS > Clear DTCs
NEXT

3.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(f) Check for DTCs.

Body Electrical > AFS > Trouble Codes

OK:

DTC B2439 and B243A are not output.

Result

Proceed to

OK

A

NG (DTC B2439 is output)

B

NG (DTC B243A is output)

C
A

USE SIMULATION METHOD TO CHECK

C

GO TO STEP 7

B

4.

CHECK HEADLIGHT UNIT LH

(a) Interchange the headlight unit LH with RH and connect the connectors.

Click here

NEXT

5.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > AFS > Clear DTCs
NEXT

6.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(f) Check for DTCs.

Body Electrical > AFS > Trouble Codes

Result

Proceed to

DTC B2439 is output

A

DTC B243A is output (for TMC Made)

B

DTC B243A is output (for TMMC Made)

C
A

REPLACE NO. 1 HEADLIGHT ECU SUB-ASSEMBLY LH

B

REPLACE HEADLIGHT UNIT LH

C

REPLACE HEADLIGHT ASSEMBLY LH

7.

CHECK HEADLIGHT UNIT RH

(a) Interchange the headlight unit RH with LH and connect the connectors.

Click here

NEXT

8.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > AFS > Clear DTCs
NEXT

9.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / AFS / Trouble Codes.

(f) Check for DTCs.

Body Electrical > AFS > Trouble Codes

Result

Proceed to

DTC B243A is output

A

DTC B2439 is output (for TMC Made)

B

DTC B2439 is output (for TMMC Made)

C
A

REPLACE NO. 1 HEADLIGHT ECU SUB-ASSEMBLY RH

B

REPLACE HEADLIGHT UNIT RH

C

REPLACE HEADLIGHT ASSEMBLY RH

10.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > HL AutoLeveling > Clear DTCs
NEXT

11.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(f) Check for DTCs.

Body Electrical > HL AutoLeveling > Trouble Codes

OK:

DTC B2439 and B243A are not output.

Result

Proceed to

OK

A

NG (DTC B2439 is output)

B

NG (DTC B243A is output)

C
A

USE SIMULATION METHOD TO CHECK

C

GO TO STEP 15

B

12.

CHECK HEADLIGHT UNIT LH

(a) Interchange the headlight unit LH with RH and connect the connectors.

Click here

NEXT

13.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > HL AutoLeveling > Clear DTCs
NEXT

14.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(f) Check for DTCs.

Body Electrical > HL AutoLeveling > Trouble Codes

Result

Proceed to

DTC B2439 is output

A

DTC B243A is output (for TMC Made)

B

DTC B243A is output (for TMMC Made)

C
A

REPLACE NO. 1 HEADLIGHT ECU SUB-ASSEMBLY LH

B

REPLACE HEADLIGHT UNIT LH

C

REPLACE HEADLIGHT ASSEMBLY LH

15.

CHECK HEADLIGHT UNIT RH

(a) Interchange the headlight unit RH with LH and connect the connectors.

Click here

NEXT

16.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > HL AutoLeveling > Clear DTCs
NEXT

17.

CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Operate the light control switch to turn on the low beam headlights and wait 10 seconds or more.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.

(f) Check for DTCs.

Body Electrical > HL AutoLeveling > Trouble Codes

Result

Proceed to

DTC B243A is output

A

DTC B2439 is output (for TMC Made)

B

DTC B2439 is output (for TMMC Made)

C
A

REPLACE NO. 1 HEADLIGHT ECU SUB-ASSEMBLY RH

B

REPLACE HEADLIGHT UNIT RH

C

REPLACE HEADLIGHT ASSEMBLY RH

    Left Low Beam Fan Malfunction (B243D,B243E)
    DESCRIPTION The No. 1 headlight ECU sub-assembly operates the low beam fan to cool the headlight LED unit in order to prevent the headlight LED unit from overheating. Illuminates the low beam headligh ...

    Height Sensor Initialization Incomplete (B2450)
    DESCRIPTION The No. 1 headlight ECU sub-assembly LH stores this DTC if initialization has not been performed after it was replaced. DTC No. Detection Item DTC Detection Condition Trouble Area ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Front Camera System: Software Incompatibility with Body Control Module Invalid/Incompatible Software Component (U032257)
    DESCRIPTION The forward recognition camera receives vehicle information from the main body ECU (multiplex network body ECU) via CAN communication. DTC U032257 is stored when the vehicle information from the main body ECU (multiplex network body ECU) and that stored in the forward recognition camera ...

    Lexus RX (RX 350L, RX450h) 2016-2025 Owners Manual > For safety and security: Theft deterrent system
    Immobilizer system The vehicle's keys have built-in transponder chips that prevent the hybrid system from starting if a key has not been previously registered in the vehicle's on-board computer. Never leave the keys inside the vehicle when you leave the vehicle. This system is designed to ...

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

    © 2025 Copyright www.lexusrx.net
    0.0136