DTC B1637: Curtain Airbag 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 Side impact sensor LH (rear wheel house)
• Side impact sensor LH (rear wheel house) 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 (AB41, AB58) between the airbag control module and Side impact sensor LH (rear wheel house).

   Is there poor contact?

   Yes  : Replace the airbag rear harness along with body harness.

   No  : Go to  2.

2. CHECK Side impact sensor LH (rear wheel house)  .
   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 Side impact sensor LH (rear wheel house) with Side impact sensor RH (rear wheel house). Ref. to AIRBAG SYSTEM>IMPACT SENSOR>REMOVAL>SIDE IMPACT SENSOR (REAR WHEEL HOUSE)
   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 B1637 or B1638 displayed? (Current code)

   Yes  : Go to  3.

   No  : Replace Side impact sensor LH (rear wheel house) that was attached on the left side at first. Ref. to AIRBAG SYSTEM>IMPACT SENSOR>REMOVAL>SIDE IMPACT SENSOR (REAR WHEEL HOUSE)

3. CHECK AIRBAG REAR HARNESS (BETWEEN AIRBAG CONTROL MODULE AND Side impact sensor LH (rear wheel house)) (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 (AB94) from seat belt pretensioner LH.
   3. Disconnect the connector (AB100) from rear seat belt pretensioner LH.
   4. Disconnect the connector (AB88) from side airbag module LH.
   5. Disconnect the connector (AB92) from curtain airbag module LH.
   6. Disconnect the connectors (AB41, AB42, AB43) from airbag control module.
   7. Connect the connector (1BF) in the test harness BF to the connectors (AB41, AB42, AB43).
   8. Disconnect the connector (AB58) from Side impact sensor LH (rear wheel house).
   9. Using a probe, measure the resistance between the connector (6BF) in test harness BF and connector (AB58). 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 

      (6BF) No. 7 - (AB58) No. 1:

      (6BF) No. 2 - (AB58) No. 2:

   Is the resistance less than 10 Ω?

   Yes  : Go to  4.

   No  : Replace the airbag rear harness along with body harness.

4. CHECK AIRBAG REAR HARNESS (BETWEEN AIRBAG CONTROL MODULE AND Side impact sensor LH (rear wheel house)) (SHORTED TO GROUND AND SHORTED BETWEEN LINES)  .

   Measure the resistance between connector (6BF) in the test harness BF and chassis ground, and the resistance between connector (6BF) terminals in the test harness BF.

   Connector & terminal 

   (6BF) No. 7 - Chassis ground:

   (6BF) No. 2 - Chassis ground:

   (6BF) No. 7 - (6BF) No. 2:

   Is the resistance 1 MΩ or more?

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

   No  : Replace the airbag rear harness along with body harness.