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Home >> Subaru >> 2024 >> Outback Base >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Airbag System (Diagnostics) (2 Of 2) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC B1864: Short In Driver's Knee Airbag

DTC B1864: Short In Driver's Knee Airbag

Diagnosis start condition: 

When the ignition voltage is 10 - 16 V.

DTC detecting condition: 

Short circuit malfunction between driver's knee airbag circuit and other circuit

Wiring diagram: 

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

G16390728Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to AIRBAG (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .
  1. CHECK POOR CONTACT OF CONNECTORS  .

    Check for poor contact of the connectors between the airbag control module and the driver's knee airbag module.

    Is there poor contact?

    Yes:  Replace the airbag harness.

    No:  Go to  2.

  2. CHECK DRIVER'S KNEE AIRBAG MODULE  .
    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 (AB86) from the driver's knee airbag module.
    3. Connect the connector (1N) in the test harness N to the connector (AB86).
    4. Connect the airbag resistor to the connector (2N) of test harness N.
    5. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Ref. to REPAIR CONTENTS>NOTE>BATTERY .

    Does the airbag warning light illuminate for six seconds and go off?

    Yes:  Replace the driver's knee airbag module. Ref. to AIRBAG SYSTEM>KNEE AIRBAG MODULE>REMOVAL .

    No:  Go to  3.

  3. CHECK AIRBAG MAIN HARNESS (DRIVER'S KNEE AIRBAG HARNESS)  .
    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 airbag resistor from test harness N.
    3. Remove the instrument panel lower cover and column cover, and disconnect the connector (AB46).
    4. Disconnect the passenger's airbag module connectors (AB83) and (AB84).
    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. Measure the resistance between connector (2N) in the test harness N and all connector terminals in the test harness BF.

      Connector & terminal 

      (2N) No. 1 - All terminals in test harness BF (except for (9BF) No. 3):

      (2N) No. 2 - All terminals in test harness BF (except for (3BF) No. 3):

    Is the resistance 1 MΩ or more?

    Yes:  Go to  4.

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

  4. CHECK AIRBAG CONTROL MODULE  .
    1. Disconnect all test harnesses.
    2. Connect all connectors.
    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 B1864 displayed? (Current code)

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

    No:  Go to  5.

  5. 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 code)

    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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