DTC A1 Front Sensor Bus Communication Error: Wiring Diagram

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Front Sensor Bus Communication Error - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE CHART

Step	Check	Yes	No
1 CHECK POOR CONTACT OF CONNECTORS. Check for poor contact of the connectors between the airbag control module and the front sub sensor.	Is there poor contact?	Replace the airbag main harness along with body harness.	Go to step 2 .
2 CHECK AIRBAG MAIN HARNESS (FRONT SENSOR BUS LH). Turn the ignition switch to OFF, disconnect the battery ground cable, and wait for 60 seconds or more. Remove the instrument panel lower cover and column cover, and disconnect the connectors (AB7) and (AB2). Remove the console front panel and disconnect the connector (AB9). Disconnect the connectors (AB6, AB17, AB18) from airbag control module. Connect the connector (1AG) in the test harness AG to the connectors (AB6, AB17, AB18). Disconnect the connector (AB13) from the front sub sensor (LH), and then connect the connector (1H) in the test harness H to connector (AB13). Measure the resistance between connector (4AG) in the test harness AG and connector (3H) in the test harness H. Connector & terminal (4AG) No. 7 - (3H) No. 5: (4AG) No. 9 - (3H) No. 6:	Is the resistance less than 10 Ω?	Go to step 3 .	Replace the airbag main harness along with body harness.
3 CHECK AIRBAG MAIN HARNESS (FRONT SENSOR BUS LH). Measure the resistance between connector (4AG) in the test harness AG and chassis ground, and the resistance between connector (4AG) terminals in the test harness AG. Connector & terminal (4AG) No. 7 - Chassis ground: (4AG) No. 9 - Chassis ground: (4AG) No. 7 - (4AG) No. 9:	Is the resistance 1 MΩ or more?	Go to step 4 .	Replace the airbag main harness along with body harness.
4 CHECK AIRBAG MAIN HARNESS (FRONT SENSOR BUS RH). Disconnect the connector (1H) in the test harness H from connector (AB13). Disconnect the connector (AB16) from the front sub sensor (RH), and then connect the connector (1H) in the test harness H to connector (AB16). Measure the resistance between connector (4AG) in the test harness AG and connector (3H) in the test harness H. Connector & terminal (4AG) No. 14 - (3H) No. 5: (4AG) No. 12 - (3H) No. 6:	Is the resistance less than 10 Ω?	Go to step 5 .	Replace the airbag main harness along with body harness.
5 CHECK AIRBAG MAIN HARNESS (FRONT SENSOR BUS RH). Measure the resistance between connector (4AG) in the test harness AG and chassis ground, and the resistance between connector (4AG) terminals in the test harness AG. Connector & terminal (4AG) No. 12 - Chassis ground: (4AG) No. 14 - Chassis ground: (4AG) No. 12 - (4AG) No. 14:	Is the resistance 1 MΩ or more?	Go to step 6 .	Replace the airbag main harness along with body harness.
6 CHECK AIRBAG CONTROL MODULE. Connect all connectors. Clear the memory. Perform the Inspection Mode. Read the DTC.	Is the same DTC displayed?	Replace the front sub sensor (LH) and front sub sensor (RH). < Ref. to REMOVAL , Front Sub Sensor. > Replace the airbag control module if not operating normally even after replacing the sensor. < Ref. to REMOVAL , Airbag Control Module. >	Go to step 7 .
7 CHECK FOR ANY OTHER DTC ON DISPLAY.	Is any other DTC displayed?	Check DTC using "List of Diagnostic Trouble Code". < Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . >	Finish the diagnosis.