DTC B2C27: Rear Sonar Harness Power Supply High/Low

Outline of diagnosis: 

Sonar sensor harness is shorted to power supply or ground.

Time needed for diagnosis: 

100 ms

Recovery conditions: 

Ignition switch OFF - ON

Wiring diagram: 

Reverse Automatic Braking Ref. to WIRING SYSTEM>REVERSE ASSIST BRAKING SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the sonar sensor connectors (L111), (L112), (L113), (L114) and the RAB control module connector (L81).
   3. Connect the disconnected connectors (L111), (L112), (L113), (L114), (L81).
   4. Turn the ignition switch to ON.
   5. Read the DTC of [Reverse Assist Braking] using the Subaru Select Monitor. Ref. to REVERSE AUTOMATIC BRAKING (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B2C27 displayed? (Current malfunction)

   Yes  : Go to  2 .

   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.
2. CHECK HARNESS BETWEEN SONAR SENSOR CONNECTOR AND RAB CONTROL MODULE CONNECTOR. (SHORT CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the sonar sensor connectors (L111), (L112), (L113), (L114) and the RAB control module connector (L81).
   3. Using a tester, measure the resistance between GND terminal of any of the sonar sensor connectors (L111), (L112), (L113), (L114) and power supply terminals.

   Connector and terminal 

   No. 1 - No. 3:

   Is the resistance 1 MΩ or more?

   Yes  : Go to  3 .

   No  : Repair or replace the short circuit in the harness between sonar sensor connector and RAB control module connector.

3. CHECK HARNESS BETWEEN SONAR SENSOR CONNECTOR AND RAB CONTROL MODULE CONNECTOR. (OPEN CIRCUIT)  .
   1. Disconnect the sonar sensor (L111), (L112), (L113), (L114) and the RAB control module connector (L81).
   2. Using a tester, measure the harness resistance between any of the sonar sensor connectors (L111), (L112), (L113), (L114) and RAB control module connector (L81).

   Connector and terminal 

   (L111) No. 1 - (L81) No. 9:

   (L112) No. 1 - (L81) No. 9:

   (L113) No. 1 - (L81) No. 9:

   (L114) No. 1 - (L81) No. 9:

   Is the resistance less than 10 Ω?

   Yes  : Go to  4 .

   No  : Repair or replace the open circuit in the harness between sonar sensor connector and RAB control module connector.

4. CHECK HARNESS BETWEEN SONAR SENSOR CONNECTOR AND RAB CONTROL MODULE CONNECTOR. (OPEN CIRCUIT)  .
   1. Disconnect the sonar sensor (L111), (L112), (L113), (L114) and the RAB control module connector (L81).
   2. Using a tester, measure the harness resistance between any of the sonar sensor connectors (L111), (L112), (L113), (L114) and RAB control module connector (L81).

   Connector and terminal 

   (L111) No. 3 - (L81) No. 22:

   (L112) No. 3 - (L81) No. 22:

   (L113) No. 3 - (L81) No. 22:

   (L114) No. 3 - (L81) No. 22:

   Is the resistance less than 10 Ω?

   Yes  : Go to  5 .

   No  : Repair or replace the open circuit in the harness between sonar sensor connector and RAB control module connector.

5. CHECK SONAR SENSOR  .
   1. Disconnect the sonar sensor connectors (L111), (L112), (L113), (L114).
   2. Using a tester, check for short circuits between each sonar sensor power supply terminal and GND terminal.

   Is there short circuit?

   Yes  : Replace the short-circuited sonar sensor. Ref. to REVERSE AUTOMATIC BRAKING>SENSOR AND HARNESS .

   No  : Replace the RAB control module. Ref. to REVERSE AUTOMATIC BRAKING>REVERSE ASSIST BRAKING CONTROL MODULE .