Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Open in IG Circuit (B242E)

DESCRIPTION

The No. 1 headlight ECU sub-assembly operates using the power source voltage input from the IG terminal and ECUB terminal.

The IG terminal power source voltage is supplied by turning the IG1 relay to ON.

The No. 1 headlight ECU sub-assembly receives engine switch on (IG) signals from the main body ECU (multiplex network body ECU) via CAN communication, compares the engine switch on (IG) signal and the power source voltage supply condition of the IG terminal and monitors the result.

for Multiple Beam Headlight

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	DTC Output from
B242E	Open in IG Circuit	The engine switch is on (IG). When the IG terminal power source voltage is 0 V (engine switch off), IG ON signals from the main body ECU (multiplex network body ECU) via CAN communication are continuously received 10 seconds or more	No. 1 headlight ECU sub-assembly LH Harness or connector	AFS

for Single Beam Headlight

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	DTC Output from
B242E	Open in IG Circuit	The engine switch is on (IG). When the IG terminal power source voltage is 0 V (engine switch off), IG ON signals from the main body ECU (multiplex network body ECU) via CAN communication are continuously received 10 seconds or more	No. 1 headlight ECU sub-assembly LH Harness or connector	HL AutoLeveling

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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 4

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) 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 B242E is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

GO TO STEP 6

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 / HL AutoLeveling / Trouble Codes.

(e) Clear the DTCs.

Body Electrical > HL AutoLeveling > Clear DTCs

NEXT

5.	CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

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

(c) 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 B242E is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

6.	INSPECT NO. 1 HEADLIGHT ECU SUB-ASSEMBLY LH (IG TERMINAL VOLTAGE)

*a	Front view of wire harness connector (to No. 1 Headlight ECU Sub-assembly LH)

(a) Disconnect the A49 No. 1 headlight ECU sub-assembly LH connector.

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A49-4 (IG) - Body ground	Engine switch on (IG)	11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

7.	CHECK HARNESS AND CONNECTOR (NO. 1 HEADLIGHT ECU SUB-ASSEMBLY LH - BODY GROUND)

(a) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A49-12 (GND) - Body ground	Always	Below 1 Ω

OK

REPLACE NO. 1 HEADLIGHT ECU SUB-ASSEMBLY LH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR