DTC B1800: Short In Driver's Airbag

Diagnosis start condition:

When the ignition voltage is 10 - 16 V.

DTC detecting condition:

Airbag main harness circuit is shorted.
Airbag module harness (driver's side) circuit is shorted.
Roll connector circuit is shorted.
Driver's 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.

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

NOTE: Prior to starting work, prepare two AIRBAG RESISTORS (98299PA040).

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

Is there poor contact?

Yes : Replace the airbag harness.

No : Go to 2 .
CHECK DRIVER'S 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. Remove the driver's airbag module.
3. Connect the connector (1N) in the test harness N to the connector (AB82).
4. Connect the airbag resistor to the connector (2N) of test harness N.
5. Connect the connector (1Q) in the test harness Q to connector (AB81).
6. Connect the airbag resistor to the connector (2Q) in the test harness Q.
7. 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 airbag module. Ref. to AIRBAG SYSTEM>DRIVER'S AIRBAG MODULE .

No : Go to 3 .
CHECK ROLL CONNECTOR AND AIRBAG MAIN HARNESS (DRIVER'S 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 passenger's airbag module connectors (AB83) and (AB84).
3. Disconnect the driver's knee airbag module connector (AB86).
4. Disconnect the airbag resistor from the connector (2N) in test harness N and from the connector (2Q) in test harness Q.
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 (2Q) terminals in test harness Q.
  Connector & terminal
  
  (2Q) No. 1 - (2Q) No. 2:
Is the resistance 1 MΩ or more?

Yes : Go to 5 .

No : Go to 4 .
CHECK AIRBAG MAIN HARNESS (DRIVER'S AIRBAG HARNESS) (SHORTED BETWEEN LINES) .
1. Remove the instrument panel lower cover and column cover, and disconnect the connector (AB46).
2. Measure the resistance between connectors (3BF) and (9BF) in test harness BF.
  Connector & terminal
  
  (3BF) No. 1 - (9BF) No. 1:
  
  Is the resistance 1 MΩ or more?
Yes : Replace the roll connector. Ref. to AIRBAG SYSTEM>ROLL CONNECTOR .

No : Replace the airbag main harness along with body harness.
CHECK AIRBAG CONTROL MODULE .
1. Disconnect the test harness BF from the connectors (AB41, AB42, AB43).
2. Connect all connectors.
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 B1800 displayed? (Current malfunction)

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

No : Go to 6 .
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?

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

No : Finish the diagnosis.