DTC B1860: Short In Driver's Knee Airbag

Diagnosis start condition: 

When the ignition voltage is 10 - 16 V.

DTC detecting condition: 

• Airbag main harness circuit is shorted.
• Driver's knee airbag module harness circuit is shorted.
• Driver's knee airbag module 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 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
   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 B1860 displayed? (Current code)

   Yes  : Go to  3.

   No  : Replace the driver's knee airbag module. Ref. to AIRBAG SYSTEM>KNEE AIRBAG MODULE>REMOVAL

3. CHECK AIRBAG MAIN HARNESS (DRIVER'S KNEE AIRBAG HARNESS) (SHORTED BETWEEN LINES)  .
   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. Disconnect the connector (AB46) from the roll connector.
   4. Disconnect the connector (AB83) from the passenger's 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. Measure the resistance between connectors (3BF) and (9BF) in test harness BF.

      Connector & terminal 

      (3BF) No. 3 - (9BF) No. 3:

   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 main harness along with body harness.