DTC B1638: Curtain Airbag Sensor LH Initialization Error

Diagnosis start condition:

When the ignition voltage is 10 - 16 V.

DTC detecting condition:

Open or short circuit in harness of side sensor bus LH.
Side airbag sensor LH and curtain airbag sensor LH are faulty.
Airbag control module is faulty.

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 .

Courtesy of SUBARU OF AMERICA, INC.

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

CHECK DTC .
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.
CHECK POOR CONTACT OF CONNECTORS .
Check for poor contact of the connectors between the airbag control module and the door sensor LH.

Is there poor contact?

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

No : Go to 3.
CHECK AIRBAG REAR HARNESS (BETWEEN SIDE AIRBAG SENSOR LH AND CURTAIN 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 ground 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 connector (AB23) in the side airbag sensor LH.
6. Connect the connector (AB23) of side airbag sensor LH and the connector (1AI) in the test harness AI.
7. Connect the connector (2AI) in the test harness AI and the connector (1V) in the test harness V.
8. Disconnect the connector (AB32) from curtain airbag sensor LH, and connect to the connector (2V) in test harness V.
9. 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 4.

No : Replace the airbag rear harness along with body harness.
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) in test harness V.

Connector & terminal

(3V) No. 1 - Chassis ground:

(3V) No. 2 - Chassis ground:

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

Is the resistance 1 MΩ or more?

Yes : Go to 5.

No : Replace the airbag rear harness along with body harness.
CHECK AIRBAG CONTROL MODULE .
1. Connect all connectors.
2. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
3. Execute the inspection mode. Ref. to AIRBAG (DIAGNOSTICS)>INSPECTION MODE .
4. Read the DTC of [Airbag] using the Subaru Select Monitor. Ref. to AIRBAG (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC B1638 displayed? (Current malfunction)

Yes : Go to 6.

No : Go to 8.
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 ground terminal from the battery.
2. Replace the curtain airbag sensor LH. Ref. to AIRBAG SYSTEM>CURTAIN AIRBAG SENSOR>REMOVAL .
3. Connect all connectors.
4. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>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 B1638 displayed? (Current malfunction)

Yes : Go to 7.

No : Go to 8.
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 ground terminal from the battery.
2. Replace the side airbag sensor LH. Ref. to AIRBAG SYSTEM>SIDE AIRBAG SENSOR>REMOVAL .
3. Connect all connectors.
4. Using the Subaru Select Monitor, perform the clear memory of [Airbag]. Ref. to COMMON (DIAG)>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 B1638 displayed? (Current malfunction)

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

No : Go to 8.
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.