DTC B1863: Short In Driver's Knee Airbag (To +B)

Diagnosis start condition:

When the ignition voltage is 10 - 16 V.

DTC detecting condition:

Airbag main harness circuit is shorted to power supply.
Knee airbag module harness circuit is shorted to power supply.
Knee airbag module is faulty.
Airbag control module is faulty.

Wiring diagram:

Airbag system Refer to WIRING SYSTEM>Airbag System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Refer to AIRBAG (DIAGNOSTICS)>General Description>CAUTION .

CHECK POOR CONTACT OF CONNECTORS .
Check for poor contact of the connectors between the airbag control module and the knee airbag module.

Is there poor contact?

Yes : Replace the airbag harness.

No : Go to 2.
CHECK 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. Refer to REPAIR CONTENTS>NOTE>BATTERY .
2. Disconnect the connector (AB86) from 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. Refer to REPAIR CONTENTS>NOTE>BATTERY .
  Does the airbag warning light illuminate for six seconds and go off?
  
  Yes : Replace the knee airbag module. Refer to AIRBAG SYSTEM>Knee Airbag Module>REMOVAL .
  
  No : Go to 3.
CHECK AIRBAG MAIN HARNESS (KNEE AIRBAG HARNESS) (SHORTED TO POWER SUPPLY) .
1. Turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the ground terminal from the battery sensor. Refer 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. Install the ground terminal to the battery sensor and turn the ignition switch to ON. Refer to REPAIR CONTENTS>NOTE>BATTERY .
8. Measure the voltage between connectors (3BF), (9BF) in the test harness BF and chassis ground.
  Connector & terminal
  
  (9BF) No. 3 (+) - Chassis ground (-):
  
  (3BF) No. 3 (+) - Chassis ground (-):
  
  Is the voltage less than 1 V?
  
  Yes : Go to 4.
  
  No : Replace the airbag main harness along with body harness.
CHECK AIRBAG CONTROL MODULE .
1. Turn the ignition switch to OFF, and wait for 60 seconds or more after disconnecting the ground terminal from the battery sensor. Refer to REPAIR CONTENTS>NOTE>BATTERY .
2. Disconnect the test harness BF from the connectors (AB41, AB42, AB43).
3. Connect all connectors.
4. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Refer to COMMON (DIAG)>CLEAR MEMORY .
5. Execute the inspection mode. Refer to AIRBAG (DIAGNOSTICS)>Inspection Mode .
6. Read the DTC of [Airbag] using the Subaru Select Monitor. Refer to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
  Is DTC B1863 displayed? (Current malfunction)
  
  Yes : Replace the airbag control module. Refer to AIRBAG SYSTEM>AIRBAG CONTROL MODULE .
  
  No : Go to 5.
CHECK FOR ANY OTHER DTC ON DISPLAY .
Read the DTC of [Airbag] using the Subaru Select Monitor. Refer to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is any other DTC displayed? (Current malfunction)

Yes : Perform the diagnosis for other displayed DTCs. Refer to AIRBAG (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)>LIST .

No : Finish the diagnosis.