DTC B27A8: Trunk/Rear Gate External Antenna Open

DTC detecting condition: 

When open circuit occurs in the harness between keyless access control module and rear exterior antenna.

Trouble symptom: 

Keyless access system does not function.

(Unable to unlock with the rear gate opener button, or unable to lock with the rear lock button. Or trunk does not open or close with the trunk opener button)

Wiring diagram: 

• Impreza model (4 door model)
  • Keyless access with push button start system Ref. to WIRING SYSTEM (IMPREZA MODEL)>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

  Courtesy of SUBARU OF AMERICA, INC.

• Impreza model (5 door model) or Crosstrek model

• Keyless access with push button start system Ref. to WIRING SYSTEM (IMPREZA MODEL)>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK LAN SYSTEM  .

   Perform the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS) (EXCEPT FOR HEV)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE . Ref. to LAN SYSTEM (DIAGNOSTICS) (HEV)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

   Is the check result OK?

   Yes:  Go to  2.

   No:  Perform the inspection according to the diagnosis for LAN system.

2. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the keyless access control module connector.
   3. Disconnect the rear exterior antenna connector.
   4. Check the connector.

   Is the check result OK?

   Yes:  Go to  3.

   No:  Repair or replace the connector.

3. CHECK POWER SUPPLY CIRCUIT  .

   Using a tester, measure the voltage between the keyless access control module connector and chassis ground.

   Connector & terminal 

   (i75) No. 4 (+) - Chassis ground (-):

   Is the voltage 9.5 - 16 V?

   Yes:  Go to  4.

   No:  Check the power supply circuit.

4. CHECK HARNESS (OPEN CIRCUIT)  .

   Using a tester, measure the resistance between the keyless access control module connector and rear exterior antenna connector, and between keyless access control module connector and chassis ground.

   Connector & terminal 

   Impreza model (4 door model) 

   (i241) No. 8 - (R299) No. 1:

   (i241) No. 7 - (R299) No. 3:

   (i241) No. 17 - Chassis ground:

   (i75) No. 20 - Chassis ground:

   Impreza model (5 door model) or Crosstrek model 

   (i241) No. 8 - (D45) No. 1:

   (i241) No. 7 - (D45) No. 3:

   (i241) No. 17 - Chassis ground:

   (i75) No. 20 - Chassis ground:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair or replace the open circuit of harness.

5. CHECK HARNESS (GROUND SHORT CIRCUIT)  .

   Using a tester, measure the resistance between the keyless access control module connector and chassis ground.

   Connector & terminal 

   (i241) No. 8 - Chassis ground:

   (i241) No. 7 - Chassis ground:

   Is the resistance 10 kΩ or more?

   Yes:  Go to  6.

   No:  Repair or replace the short circuit of the harness.

6. CHECK DTC  .
   1. Connect the keyless access control module connector.
   2. Turn the ignition switch to ON.
   3. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   4. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B27A8 displayed? (Current malfunction)

   Yes:  Go to  7.

   No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE:

   In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause. 

7. CHECK KEYLESS ACCESS CONTROL MODULE  .
   1. Replace the rear exterior antenna with the rear interior antenna. Ref. to SECURITY AND LOCKS>KEYLESS ACCESS INDOOR ANTENNA . Ref. to SECURITY AND LOCKS>KEYLESS ACCESS OUTDOOR ANTENNA .
   2. Turn the ignition switch to ON.
   3. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   4. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B27A8 displayed? (Current malfunction)

   Yes:  Replace the keyless access control module. Ref. to SECURITY AND LOCKS>KEYLESS ACCESS CONTROL MODULE .

   No:  Malfunction occurred in the rear external antenna.