Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Automatic High Beam System (B124B)

Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual / Vehicle Exterior / Lighting (ext) / Lighting System (w/ Automatic Headlight Beam Level Control System) / Automatic High Beam System (B124B)

DESCRIPTION

The main body ECU (multiplex network body ECU) determines the status of the automatic high beam system based on the automatic high beam system signal from the forward recognition camera.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

DTC Output from

B124B

Automatic High Beam System

Malfunction in automatic high beam system
  • Front camera system
  • Dynamic radar cruise control system
  • Lane control system
  • Road sign assist system*
  • Pre-collision system
  • SFI system
  • Vehicle stability control system
  • CAN communication system
  • Forward recognition camera
  • Main body ECU (multiplex network body ECU)

Main Body
  • *: w/ Road Sign Assist System

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • The lighting system uses the CAN communication system. Inspect the communication functions by following How to Proceed with Troubleshooting. Troubleshoot the automatic high beam system after confirming that the communication systems are functioning properly.

    Click here

  • Before replacing the main body ECU (multiplex network body ECU), refer to Registration.

    Click here

HINT:

If the forward recognition camera stores a DTC for a malfunction of any of the following, this DTC will be stored simultaneously.
  • Speed sensor
  • Yaw rate sensor
  • Millimeter wave radar sensor
  • CAN communication system

PROCEDURE

1.

CHECK FOR DTC (HEALTH CHECK)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: System Select / Health Check.

(e) Check for DTCs.

Result

Proceed to

Only DTC B124B is output

A

DTC B124B and other DTCs are output

B
B

GO TO OTHER DTC CHART
A

2.

CHECK FRONT CAMERA SYSTEM

(a) Check if a dynamic radar cruise control system, lane control system, road sign assist system* or pre-collision system warning message is displayed on the multi-information display.

Click here

OK:

No dynamic radar cruise control system, lane control system, road sign assist system* or pre-collision system warning messages are displayed.

  • *: w/ Road Sign Assist System
OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

GO TO FRONT CAMERA SYSTEM

    Vehicle Control History
    VEHICLE CONTROL HISTORY CHECK VEHICLE CONTROL HISTORY HINT: The vehicle control history data stores the history of the reject function and system protection operations. The number of occurrences, ...

    Light Sensor Circuit (B1244)
    DESCRIPTION The automatic light control sensor detects ambient light. The sensor creates an electrical signal based on the amount of light detected, and sends the signal to the main body ECU (multiple ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Back Door Lock: Inspection
    INSPECTION PROCEDURE 1. INSPECT BACK DOOR LOCK ASSEMBLY *a Clockwise *b Counterclockwise *c Over-latch *d Full-latch *e Half-latch *f Open-latch *g Component without harness connected (Back Door Lock Assembly) (a) Apply battery voltage to the door lock mo ...

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Parking Assist Ecu: Components
    COMPONENTS ILLUSTRATION *1 COWL SIDE TRIM BOARD RH *2 FRONT DOOR SCUFF PLATE RH *3 GLOVE COMPARTMENT DOOR ASSEMBLY *4 INSTRUMENT PANEL GARNISH RH *5 LOWER NO. 1 INSTRUMENT PANEL FINISH PANEL *6 NO. 2 INSTRUMENT PANEL UNDER COVER SUB-ASSEMBLY *7 PARKING ASSIST ECU ...

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

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

    © 2026 Copyright www.lexusrx.net
    0.0111