Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: GSW Terminal Circuit Malfunction (B1243)

DESCRIPTION

If the collision door lock release function does not operate normally, or an open or short in the GSW input circuit of the main body ECU (multiplex network body ECU) is detected, DTC B1243 will be stored.

HINT:

If DTC B1243 is stored, the automatic door lock function, and collision door lock release function will be prohibited.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B1243	GSW Terminal Circuit Malfunction	A malfunction occurs in the GSW input circuit of the main body ECU (multiplex network body ECU).	Main body ECU (multiplex network body ECU) Airbag sensor assembly Wire harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK DTC OUTPUT

(a) Clear the DTCs.

Click here

Body Electrical > Main Body > Clear DTCs

(b) Recheck for DTCs.

Body Electrical > Main Body > Trouble Codes

OK:

DTC B1243 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

2.	CHECK MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) (GSW VOLTAGE)

(a) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

NOTICE:

Turning the engine switch on (IG) with the airbag sensor assembly connector disconnected causes other DTCs to be stored. Clear the DTCs after performing this inspection.

(b) Disconnect the J142 airbag sensor assembly connector.

(c) Connect the cable to the negative (-) battery terminal.

(d) Measure the voltage according to the value(s) in the table below. Standard Voltage: Tester Connection Condition Specified Condition J142-25 (GSW) - Body ground Engine switch on (IG) 4.5 to 5.5 V

*a Front view of wire harness connector (to Airbag Sensor Assembly)

NG

GO TO STEP 5

OK

3.	REPLACE AIR BAG SENSOR ASSEMBLY

(a) Replace the airbag sensor assembly.

Click here

NEXT

4.	CHECK DTC OUTPUT

(a) Clear the DTCs.

Click here

Body Electrical > Main Body > Clear DTCs

(b) Recheck for DTCs.

Body Electrical > Main Body > Trouble Codes

OK:

DTC B1243 is not output.

OK

END (AIRBAG SENSOR ASSEMBLY WAS DEFECTIVE)

NG

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

5.	CHECK HARNESS AND CONNECTOR (AIRBAG SENSOR ASSEMBLY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the 2A instrument panel junction block assembly connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J142-25 (GSW) - 2A-7	Always	Below 1 Ω
2A-7 or J142-25 (GSW) - Body ground	Always	10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

6.	INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

(a) Remove the instrument panel junction block assembly.

Click here

(b) Remove the main body ECU (multiplex network body ECU).

*a

Component without harness connected (Instrument Panel Junction Block Assembly)

-

-

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
MB-24 (GSW) - 2A-7	Always	Below 1 Ω

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY