DTC B2351: Rear Radar Lost Communication Between Master And Slave

DTC detecting condition: 

• Defective harness for CAN communication between radar sensor LH - radar sensor RH.
• Defective radar sensor

Trouble symptom: 

• All functions of BSD/RCTA stop.
• Fail icon is displayed in the combination meter LCD display.
• Failure-related notification is displayed for approx. two seconds on LCD display in the combination meter.

Wiring diagram: 

Blind Spot Detection/Rear Cross Traffic Alert system Ref. to WIRING SYSTEM>BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor, read the DTCs of [Blind Spot Detection/Rear Cross Traffic Alert (RH)] or [Blind Spot Detection/Rear Cross Traffic Alert (LH)]. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 
      • Blind Spot Detection/Rear Cross Traffic Alert (RH)
      • Blind Spot Detection/Rear Cross Traffic Alert (LH)

   Is DTC B2351 displayed? (Current code)

   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 (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the radar sensor connectors LH and RH.
   3. Using a tester, measure the resistance between radar sensor LH connector (harness side) and radar sensor RH connector (harness side).

      Connector & terminal 

      (L107) No. 1 - (R104) No. 1:

      (L107) No. 6 - (R104) No. 6:

   Is the resistance less than 1 Ω?

   Yes  : Go to  3.

   No  : Repair the open circuit of the harness between radar sensor LH connector and radar sensor RH connector.

3. CHECK HARNESS (SHORT BETWEEN LINES, GROUND SHORT CIRCUIT)  .

   Using a tester, measure the resistance between radar sensor LH connectors (harness side) and the resistance between radar sensor LH connector (harness side) and chassis ground.

   Connector & terminal 

   (L107) No. 1 - (L107) No. 6:

   (L107) No. 1 - Chassis ground:

   (L107) No. 6 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes  : Go to  4.

   No  : Repair the short circuit of the harness between radar sensor LH connector and radar sensor RH connector.

4. CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY)  .
   1. Turn the ignition switch to ON.
   2. Using a tester, measure the voltage between radar sensor LH connector (harness side) and chassis ground.

      Connector & terminal 

      (L107) No. 1 (+) - Chassis ground (-):

      (L107) No. 6 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes  : Go to  5.

   No  : Repair the short circuit to power supply in the harness between radar sensor LH connector and radar sensor RH connector.

5. CHECK RADAR SENSOR. (INTERNAL IMPEDANCE)  .

   Using a tester, measure the internal impedance between radar sensor LH and radar sensor RH terminals.

   Terminals 

   Radar sensor LH 

   No. 1 - No. 6:

   Radar sensor RH 

   No. 1 - No. 6:

   Is the resistance approximately 120 Ω?

   Yes  : Go to  6.

   No  : Replace the radar sensor LH or radar sensor RH. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>RADAR SENSOR

6. CHECK BSD/RCTA  .
   1. Restore the vehicle to its original state.
   2. Using the Subaru Select Monitor, perform the clear memory of [Blind Spot Detection/Rear Cross Traffic Alert (RH)] or [Blind Spot Detection/Rear Cross Traffic Alert (LH)]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
      • Blind Spot Detection/Rear Cross Traffic Alert (RH)
      • Blind Spot Detection/Rear Cross Traffic Alert (LH)
   3. Perform the inspection mode. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT (DIAGNOSTICS)>INSPECTION MODE 

   Is DTC B2351 displayed? (Current code)

   Yes  : Replace the radar sensor on the side that displayed the DTC. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>RADAR SENSOR

   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.