DTC B1243: GSW Terminal Circuit Malfunction: Procedure

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

CHECK HARNESS AND CONNECTOR (BODY ECU - AIRBAG SENSOR ASSEMBLY)
1. Disconnect connector "D23" of the airbag sensor assembly and connector "IE" of the body ECU.
2. Check for an open or short circuit in the harness and connector between the airbag sensor assembly and body ECU.
  OK
  
  There is no open or short circuit in the wire harness.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step
INSPECT BODY ECU
1. Check that DTC B1243 is indicated when another body ECU in good condition is installed.
2. Check if DTC B1243 is indicated after replacing the body ECU.
  OK
  
  DTCs B1243 is not indicated.
NG → REPLACE AIRBAG SENSOR ASSEMBLY

OK → REPLACE BODY ECU (ORIGINAL BODY ECU IS FAILURE)