DTC B1243: GSW Terminal Circuit Malfunction [06/2018 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Main Body / Trouble Codes.
5. Clear the DTCs.

   Body Electrical > Main Body > Clear DTCs 

6. Recheck for DTCs.

   Body Electrical > Main Body > Trouble Codes 

   OK

   DTC B1243 is not output.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [06/2018 - ] 

Result: 

NG 

See step  2

1. Disconnect the cable from the negative (-) battery terminal.
   WARNING:

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

   NOTE:

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

2. Disconnect the G64 airbag ECU assembly connector.
3. Connect the cable to the negative (-) battery terminal.
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   G64-25 (GSW) - Body ground	Engine switch on (IG)	4.3 to 5.5 V

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  5

Result: 

OK 

See step  3

1. Disconnect the cable from the negative (-) battery terminal.
   WARNING:

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

2. Replace the airbag ECU assembly.

   Refer to REMOVAL [06/2018 - 08/2020] , or refer to REMOVAL [08/2020 - 08/2021] , or refer to REMOVAL [08/2021 - 09/2022] , or refer to REMOVAL [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  4

1. Clear the DTCs.

   Body Electrical > Main Body > Clear DTCs 

2. Recheck for DTCs.

   Body Electrical > Main Body > Trouble Codes 

   OK

   DTC B1243 is not output.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

END (AIRBAG ECU ASSEMBLY WAS DEFECTIVE) 

Result: 

NG 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [06/2018 - 08/2021]  , or refer to  REMOVAL [08/2021 - 09/2022]  , or refer to  REMOVAL [09/2022 - ] 

1. Disconnect the cable from the negative (-) battery terminal.
   WARNING:

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

2. Disconnect the 3A instrument panel junction block assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   G64-25 (GSW) - 3A-7	Always	Below 1 Ω
   3A-7 or G64-25 (GSW) - Other terminals and body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  6

1. Remove the instrument panel junction block assembly.

   Refer to REMOVAL [06/2018 - 08/2021] , or refer to REMOVAL [08/2021 - 09/2022] , or refer to REMOVAL [09/2022 - ]

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component without harness connected (Instrument Panel Junction Block Assembly)

   -

   -

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   MB-24 (GSW) - 3A-7	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [06/2018 - 08/2021]  , or refer to  REMOVAL [08/2021 - 09/2022]  , or refer to  REMOVAL [09/2022 - ] 

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [06/2018 - 08/2021]  , or refer to  REMOVAL [08/2021 - 09/2022]  , or refer to  REMOVAL [09/2022 - ]