DTC B27A5: Front Internal Antenna Open

DTC detecting condition: 

When open circuit occurs in the harness between keyless access control module and front interior antenna.

Trouble symptom: 

The keyless access with push button start system does not operate. (When the access key is in the front area of the passenger room)

Wiring diagram: 

Keyless access with push button start system. Refer to WIRING SYSTEM (IMPREZA MODEL)>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Refer to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Refer 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. Refer to LAN SYSTEM (DIAGNOSTICS) (EXCEPT FOR HEV)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE . Refer 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. Disconnect the keyless access control module connector.
   2. Disconnect the front interior antenna connector.
   3. 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 front interior antenna connector, and between keyless access control module connector and chassis ground.

   Connector & terminal 

   (i241) No. 25 - (i71) No. 1:

   (i241) No. 12 - (i71) 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. 25 - Chassis ground:

   (i241) No. 12 - 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. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (diag)>DIAGNOSTIC TROUBLE CODE (DTC) .
   3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B27A5 displayed?

      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 FRONT INTERIOR ANTENNA. 
   1. Replace the rear interior antenna with the front interior antenna. Refer to SECURITY AND LOCKS>KEYLESS ACCESS INDOOR ANTENNA .
   2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B27A5 displayed?

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

   No:  Malfunction occurred in the front interior antenna.