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). |
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WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
Click here
Click here
PROCEDURE
1. | CHECK DTC OUTPUT |
(a) Clear the DTCs.
Click here
(b) Recheck for DTCs.
Body Electrical > Main Body > Trouble CodesOK:
DTC B1243 is not output.
OK | ![]() | USE SIMULATION METHOD TO CHECK |
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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:
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NG | ![]() | GO TO STEP 5 |
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3. | REPLACE AIR BAG SENSOR ASSEMBLY |
(a) Replace the airbag sensor assembly.
Click here
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4. | CHECK DTC OUTPUT |
(a) Clear the DTCs.
Click here
(b) Recheck for DTCs.
Body Electrical > Main Body > Trouble CodesOK:
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 |
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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 |
Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Airbag System: How To Proceed With Troubleshooting
CAUTION / NOTICE / HINT HINT:
Use the following procedure to troubleshoot the airbag system.
*: Use the Techstream.
PROCEDURE 1. VEHICLE BROUGHT TO WORKSHOP
NEXT 2. CUSTOMER PROBLEM ANALYSIS (a) Confirm problem symptoms. Click here
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