Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: 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 headlights and continuously operates the low beam fan.

The No. 1 headlight ECU sub-assembly monitors the pulse signals from the FANP terminal when the low beam fans are operating.

HINT:

If B243D or B243E is output, the No. 1 headlight ECU sub-assembly performs low beam headlight dimming control.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	DTC Output from
B243D	Left Low Beam Fan Malfunction	All of the following conditions are met: Engine switch on (IG) Low beam headlights on Fan speed signals from the low beam fan of less than 1600 rpm are continuously detected 120 seconds or more	No. 1 headlight ECU sub-assembly LH Headlight unit LH	AFS
B243E	Right Low Beam Fan Malfunction	All of the following conditions are met: Engine switch on (IG) Low beam headlights on Fan speed signals from the low beam fan of less than 1600 rpm are continuously detected 10 seconds or more	No. 1 headlight ECU sub-assembly RH Headlight unit RH	AFS

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.

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

2.	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 120 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 B243D and B243E are not output.

Result	Proceed to
OK	A
NG (DTC B243D is output)	B
NG (DTC B243E is output)	C

A

USE SIMULATION METHOD TO CHECK

C

GO TO STEP 6

B

3.	CHECK HEADLIGHT UNIT LH

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

Click here

NEXT

4.

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

5.	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 120 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 B243D is output	A
DTC B243E is output (for TMC Made)	B
DTC B243E 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

6.	CHECK HEADLIGHT UNIT RH

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

Click here

NEXT

7.

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

8.	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 120 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 B243E is output	A
DTC B243D is output (for TMC Made)	B
DTC B243D 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