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Home >> Subaru >> 2021 >> Crosstrek Limited >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Airbag System (Diagnostics) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC B1647: Side Satellite Sensor Bus LH Lost Communication

DTC B1647: Side Satellite Sensor Bus LH Lost Communication

Diagnosis start condition: 

When the ignition voltage is 10 - 16 V.

DTC detecting condition: 

Wiring diagram: 

Airbag system Ref. to WIRING SYSTEM (IMPREZA MODEL)>AIRBAG SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR (HEV))>AIRBAG SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>AIRBAG SYSTEM>WIRING DIAGRAM .

G11256509Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to AIRBAG (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .
  1. CHECK DTC  .
    1. Turn the ignition switch to ON.
    2. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1627 or B1628 displayed? (Current malfunction)

    Yes:  Perform the diagnosis for the displayed DTC B1627 or B1628. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1627 SIDE AIRBAG SENSOR LH LOST COMMUNICATION . Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1628 SIDE AIRBAG SENSOR LH INITIALIZATION ERROR .

    No:  Go to  2.

  2. CHECK DTC  .

    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 malfunction)

    Yes:  Perform the diagnosis for the displayed DTC B1637 or B1638. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1637 CURTAIN AIRBAG SENSOR LH LOST COMMUNICATION . Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1638 CURTAIN AIRBAG SENSOR LH INITIALIZATION ERROR .

    No:  Go to  3.

  3. CHECK DTC  .

    Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1697 or B1698 displayed? (Current malfunction)

    Yes:  Perform the diagnosis for the displayed DTC B1697 or B1698. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1697 LOST COMMUNICATION WITH DOOR SENSOR LH . Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC B1698 DOOR SENSOR LH INITIALIZATION INCOMPLETE .

    No:  Go to  4.

  4. CHECK POOR CONTACT OF CONNECTORS  .

    Check for poor contact of the connectors between the airbag control module and the front door impact sensor LH.

    Is there poor contact?

    Yes:  Replace the airbag rear harness and the door harness.

    No:  Go to  5.

  5. CHECK AIRBAG REAR HARNESS (BETWEEN AIRBAG CONTROL MODULE AND SIDE AIRBAG 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>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the negative terminal from the battery.
    2. Disconnect the connector (AB21) from seat belt pretensioner LH.
    3. Disconnect the connector (AB31) from curtain airbag module LH.
    4. Disconnect the connector (AB19) of the side airbag module LH.
    5. Disconnect the connectors (AB6, AB17, AB18) from airbag control module.
    6. Connect the connector (1AG) in the test harness AG to the connectors (AB6, AB17, AB18).
    7. Disconnect the connector (AB23) from the side airbag sensor LH.
    8. Connect the connector (2V) in the test harness V to the connector (AB23).
    9. Measure the resistance between connector (5AG) in the test harness AG and connector (3V) in the test harness V.

      Connector & terminal 

      (5AG) No. 10 - (3V) No. 1:

      (5AG) No. 8 - (3V) No. 2:

    Is the resistance less than 10 Ω?

    Yes:  Go to  6.

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

  6. CHECK AIRBAG REAR HARNESS (BETWEEN AIRBAG CONTROL MODULE AND SIDE AIRBAG SENSOR LH)  .

    Measure the resistance between connector (3V) in test harness V and chassis ground, and the resistance between connector (3V) terminals.

    Connector & terminal 

    (3V) No. 1 - Chassis ground:

    (3V) No. 2 - Chassis ground:

    (3V) No. 1 - (3V) No. 2:

    Is the resistance 1 Ω or more?

    Yes:  Go to  7.

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

  7. CHECK AIRBAG REAR HARNESS (BETWEEN SIDE AIRBAG SENSOR AND CURTAIN AIRBAG SENSOR LH)  .
    1. Disconnect the connector (2V) in the test harness V from the connector (AB23) of side airbag sensor LH.
    2. Connect the connector (AB23) of side airbag sensor LH and the connector (1AI) in the test harness AI.
    3. Connect the connector (2AI) in the test harness AI and the connector (1V) in the test harness V.
    4. Disconnect the connector (AB32) from curtain airbag sensor LH, and connect the connector (2V) in test harness V to connector (AB32).
    5. Measure the resistance between connector (3V) terminals in the test harness V.

      Connector & terminal 

      (3V) No. 2 - (3V) No. 6:

      (3V) No. 1 - (3V) No. 7:

    Is the resistance less than 10 Ω?

    Yes:  Go to  8.

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

  8. CHECK AIRBAG REAR HARNESS (BETWEEN SIDE AIRBAG SENSOR AND CURTAIN AIRBAG SENSOR LH)  .

    Measure the resistance between connector (3V) in test harness V and chassis ground, and the resistance between connector (3V) terminals in test harness V.

    Connector & terminal 

    (3V) No. 2 - Chassis ground:

    (3V) No. 1 - Chassis ground:

    (3V) No. 1 - (3V) No. 2:

    Is the resistance 1 Ω or more?

    Yes:  Go to  9.

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

  9. CHECK AIRBAG REAR HARNESS AND DOOR HARNESS (BETWEEN CURTAIN AIRBAG SENSOR LH AND DOOR SENSOR LH)  .
    1. Disconnect the connector (AB58) from the front door impact sensor LH, and connect the connector (1H) in the test harness H to connector (AB58).
    2. Measure the resistance between connector (3V) in the test harness V and connector (3H) in the test harness H.

      Connector & terminal 

      (3V) No. 4 - (3H) No. 5:

      (3V) No. 5 - (3H) No. 6:

    Is the resistance less than 10 Ω?

    Yes:  Go to  10.

    No:  Check the door harness, and if any fault is found, replace the harness. If there is no fault, replace the airbag rear harness together with body harness.

  10. CHECK AIRBAG REAR HARNESS AND DOOR HARNESS (BETWEEN CURTAIN AIRBAG SENSOR LH AND DOOR SENSOR LH)  .

    Measure the resistance between connector (3V) in test harness V and chassis ground, and the resistance between connector (3V) terminals in test harness V.

    Connector & terminal 

    (3V) No. 4 - Chassis ground:

    (3V) No. 5 - Chassis ground:

    (3V) No. 4 - (3V) No. 5:

    Is the resistance 1 Ω or more?

    Yes:  Go to 11.

    No:  Check the door harness, and if any fault is found, replace the harness. If there is no fault, replace the airbag rear harness together with body harness.

  11. CHECK AIRBAG CONTROL MODULE  .
    1. Connect all connectors.
    2. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, connect the battery negative terminal and turn the ignition switch to ON.
    3. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
    4. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE .
    5. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1647 displayed? (Current malfunction)

    Yes:  Go to  12.

    No:  Go to  15.

  12. REPLACE SIDE AIRBAG SENSOR LH AND CHECK AIRBAG CONTROL MODULE AFTER REPLACEMENT  .
    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>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the negative terminal from the battery.
    2. Replace the side airbag sensor LH. Ref. to AIRBAG SYSTEM>SIDE AIRBAG SENSOR>REMOVAL .
    3. Connect all connectors.
    4. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, connect the battery negative terminal and turn the ignition switch to ON.
    5. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
    6. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE .
    7. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1647 displayed? (Current malfunction)

    Yes:  Go to  13.

    No:  Go to  15.

  13. REPLACE CURTAIN AIRBAG SENSOR LH AND CHECK AIRBAG CONTROL MODULE AFTER REPLACEMENT  .
    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>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the negative terminal from the battery.
    2. Replace the curtain airbag sensor LH. Ref. to AIRBAG SYSTEM>CURTAIN AIRBAG SENSOR>REMOVAL .
    3. Connect all connectors.
    4. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, connect the battery negative terminal and turn the ignition switch to ON.
    5. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
    6. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE .
    7. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1647 displayed? (Current malfunction)

    Yes:  Go to  14.

    No:  Go to  15.

  14. REPLACE FRONT DOOR IMPACT SENSOR LH AND CHECK AIRBAG CONTROL MODULE AFTER REPLACEMENT  .
    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>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the negative terminal from the battery.
    2. Replace the front door impact sensor LH. Ref. to AIRBAG SYSTEM>FRONT DOOR IMPACT SENSOR>REMOVAL .
    3. Connect all connectors.
    4. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>REPAIR CONTENTS>NOTE>BATTERY .
      NOTE: For the hybrid model, connect the battery negative terminal and turn the ignition switch to ON.
    5. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
    6. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE .
    7. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1647 displayed? (Current malfunction)

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

    No:  Go to  15.

  15. CHECK FOR ANY OTHER DTC ON DISPLAY  .

    Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is any other DTC displayed? (Current malfunction)

    Yes:  Perform the diagnosis for other displayed DTCs. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

    No:  Finish the diagnosis.

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