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DTC U0231: Lost Communication With Rain Light Sensor

DTC detecting condition: 

Data does not arrive from rain sensor.

Trouble symptom: 

Auto wiper and auto light do not operate properly.

Wiring diagram: 

Front wiper and washer system Ref. to WIRING SYSTEM>FRONT WIPER AND WASHER SYSTEM>WIRING DIAGRAM .

G16447364Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BODY CONTROL (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .
  1. CHECK DTC  .
    1. Turn the ignition switch to ON.
    2. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC U0231 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 CONTROL MODULE  .

    Using Subaru Select Monitor, confirm that the customization items of [Body Control] correspond to the vehicle. Ref. to BODY CONTROL (DIAGNOSTICS)>CUSTOMIZE .

    Is the customization item [Rain drop Detection Sensor Setting] set to [Exist]?

    Yes:  Go to  3.

    No:  Set the customization item corresponding to the vehicle.

  3. CHECK DTC  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the rain sensor connector and the body integrated unit connector.
    3. Connect the disconnected connectors.
    4. Turn the ignition switch to ON.
    5. Read the DTC of the LAN system using the Subaru Select Monitor. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC U0231 displayed? (Current code)

    Yes:  Go to  4.

    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.
  4. CHECK HARNESS  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the rain sensor connector and the body integrated unit connector.
    3. Using the tester, measure the resistance between terminals.

      Connector & terminal 

      (R352) No. 1 - (i81) No. 18:

      (R352) No. 4 - Chassis ground:

    Is the resistance less than 10 Ω?

    Yes:  Go to  5.

    No:  Repair the open circuit of harness.

  5. CHECK HARNESS  .
    1. Disconnect the power rear gate control module connector. (With power rear gate)
    2. Disconnect the sunroof unit connector and the sunshade control module connector. (With sunroof)
    3. Using the tester, measure the resistance between terminals.

      Connector & terminal 

      (R352) No. 1 - Chassis ground:

    Is the resistance 10 kΩ or more?

    Yes:  Go to  6.

    No:  Repair the shorted portion of harness.

  6. CHECK HARNESS  .
    1. Turn the ignition switch to ON.
    2. Using the tester, measure the voltage between terminals.

      Connector & terminal 

      (R352) No. 1 (+) - Chassis ground (-):

    Is the voltage less than 1 V?

    Yes:  Go to  7.

    No:  Repair the shorted portion of harness.

  7. CHECK HARNESS  .
    1. Turn the ignition switch to ON.
    2. Using the tester, measure the voltage between terminals.

      Connector & terminal 

      (R352) No. 5 (+) - Chassis ground (-):

    Is the voltage 9 V or more?

    Yes:  Go to  8.

    No:  Repair the open circuit of harness.

  8. CHECK CONTROL MODULE  .
    1. Turn the ignition switch to OFF.
    2. Replace the rain sensor with a properly functioning part. Ref. to GLASS/WINDOWS/MIRRORS>RAIN SENSOR .
    3. Turn the ignition switch to ON.
    4. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC U0231 displayed? (Current code)

    Yes:  Replace the body integrated unit. Ref. to SECURITY AND LOCKS>BODY INTEGRATED UNIT .

    No:  For model without power rear gate or sunroof, malfunction occurred in the rain sensor. For model with power rear gate or with sunroof, Go to  9.

  9. CHECK CONTROL MODULE  .
    NOTE: For models without power rear gate, Go to  10.
    1. Turn the ignition switch to OFF.
    2. Connect the power rear gate control module connector.
    3. Turn the ignition switch to ON.
    4. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC U0231 displayed? (Current code)

    Yes:  Replace the power rear gate control module. Ref. to POWER REAR GATE SYSTEM>POWER REAR GATE CONTROL MODULE .

    No:  Go to  10.

  10. CHECK CONTROL MODULE  .
    1. Turn the ignition switch to OFF.
    2. Connect the sunroof unit connector and the sunshade control module connector.
    3. Turn the ignition switch to ON.
    4. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC U0231 displayed? (Current code)

    Yes:  Replace the sunroof unit. Ref. to SUNROOF/T-TOP/CONVERTIBLE TOP (SUNROOF)>SUNROOF MOTOR .

    No:  Malfunction occurred in the rain sensor.

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