DTC B1617: Front Sub Sensor LH Lost Communication

Diagnosis start condition: 

When the ignition voltage is 10 - 16 V.

DTC detecting condition: 

• Open or short circuit in harness of Front impact sensor bus LH
• Front impact sensor LH is faulty.
• Airbag control module is faulty.

Wiring diagram: 

Airbag system Ref. to WIRING SYSTEM>AIRBAG SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK POOR CONTACT OF CONNECTORS  .

   Check for poor contact of the connectors (AB42, B42, AB52) between the airbag control module and Front impact sensor LH.

   Is there poor contact?

   Yes  : Replace the bulkhead harness or airbag main harness.

   No  : Go to  2.

2. CHECK Front impact sensor LH  .
   1. Turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the ground terminal from the battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY
   2. Replace Front impact sensor LH with Front impact sensor RH. Ref. to AIRBAG SYSTEM>IMPACT SENSOR>REMOVAL>FRONT IMPACT SENSOR
   3. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>NOTE>BATTERY
   4. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
   5. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE 
   6. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 

   Is DTC B1617 or B1618 displayed? (Current code)

   Yes  : Go to  3.

   No  : Replace Front impact sensor LH that was attached on the left side at first. Ref. to AIRBAG SYSTEM>IMPACT SENSOR>REMOVAL>FRONT IMPACT SENSOR

3. CHECK AIRBAG MAIN HARNESS (Front impact sensor BUS LH) (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the ground terminal from the battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY
   2. Disconnect the connector (AB46) from the roll connector.
   3. Disconnect the connector (AB83) from the passenger's airbag module.
   4. Disconnect the connector (AB86) from the driver's knee airbag module.
   5. Disconnect the connectors (AB41, AB42, AB43) from airbag control module.
   6. Connect the connector (1BF) in the test harness BF to the connectors (AB41, AB42, AB43).
   7. Disconnect the connector (AB52) from Front impact sensor LH.
   8. Using a probe, measure the resistance between the connectors (2BF), (8BF) in test harness BF and connector (AB52). Ref. to AIRBAG (DIAGNOSTICS)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE PROBE 
      CAUTION:

      When measuring the resistance, make sure to insert the probe from the inspection hole of the connector. Also, do not insert the probe forcibly. 

      Connector & terminal 

      (8BF) No. 5 - (AB52) No. 1:

      (2BF) No. 10 - (AB52) No. 2:

   Is the resistance less than 10 Ω?

   Yes  : Go to  4.

   No  : Check the bulkhead harness or airbag main harness, and replace the faulty harness.

4. CHECK AIRBAG MAIN HARNESS (Front impact sensor BUS LH) (SHORTED TO GROUND AND SHORTED BETWEEN LINES)  .

   Measure the resistance between connectors (2BF), (8BF) in the test harness BF and chassis ground, and the resistance between the connectors (2BF) and (8BF) in the test harness BF.

   Connector & terminal 

   (8BF) No. 5 - Chassis ground:

   (2BF) No. 10 - Chassis ground:

   (8BF) No. 5 - (2BF) No. 10:

   Is the resistance 1 MΩ or more?

   Yes  : Replace the airbag control module. Ref. to AIRBAG SYSTEM>AIRBAG CONTROL MODULE>REMOVAL

   No  : Check the bulkhead harness or airbag main harness, and replace the faulty harness.