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:

BSD/RCTA system Ref. to WIRING SYSTEM (IMPREZA MODEL)>BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .

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 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.
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 RH connector (harness side) and radar sensor LH connector (harness side).
  Connector and terminal
  
  (R25) No. 1 - (R61) No. 1:
  
  (R25) No. 6 - (R61) No. 6:
Is the resistance less than 1 Ω?

Yes: Go to 3.

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

(R25) No. 1 - (R25) No. 6:

(R25) No. 1 - Chassis ground:

(R25) No. 6 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Repair the short circuit of harness between radar sensor RH connector and radar sensor LH connector.
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 and terminal
  
  (R25) No. 1 (+) - Chassis ground (-):
  
  (R25) No. 6 (+) - Chassis ground (-):
Is the voltage less than 1 V?

Yes: Go to 5.

No: Repair the short to power supply in harness between radar sensor RH connector and radar sensor LH connector.
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 RH or radar sensor LH. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT>RADAR SENSOR .
CHECK BSD/RCTA .
1. Restore the vehicle to its original state.
2. Turn the ignition switch to ON.
3. 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 (DIAG)> CLEAR MEMORY .
  - Blind Spot Detection/Rear Cross Traffic Alert(RH)
  - Blind Spot Detection/Rear Cross Traffic Alert(LH)
4. Perform the inspection mode. Ref. to BLIND SPOT DETECTION/REAR CROSS TRAFFIC ALERT (DIAGNOSTICS)>INSPECTION MODE .
Is DTC B2351 displayed? (Current malfunction)

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.